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The Mendelian inheritance pattern of acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria is autosomal dominant, but the clinical phenotype is heterogeneous. Within the general population, penetrance is low, but among first-degree relatives of a symptomatic proband, penetrance is higher. These observations suggest that genetic factors, in addition to mutation of the specific enzyme of the biosynthetic pathway of heme, contribute to the clinical phenotype. Recent studies by others suggested that the genotype of the transporter protein ABCB6 contribute to the porphyria phenotype. Identifying the molecule(s) that are transported by ABCB6 has been problematic and has led to uncertainty with respect to how or if variants/mutants contribute to phenotypic heterogeneity. Knockout mouse models of Abcb6 have not provided a direction for investigation as homozygous knockout animals do not have a discrete phenotype. To address the proposed link between ABC6 genotype and porphyria phenotype, a large cohort of patients with acute hepatic porphyria and erythropoietic protoporphyria was analyzed. Our studies showed that ABCB6 genotype did not correlate with disease severity. Therefore, genotyping of ABCB6 in patients with acute hepatic porphyria and erythropoietic protoporphyria is not warranted.

Purpose: Patients with erythropoietic protoporphyria (EPP), a severe painful photodermatosis, experience prodromal sensations when exposed to sunlight, which are the “warning signals” to exit the sun, as prolonged exposure causes an excruciatingly painful phototoxic attack. The unique prodromal cutaneous sensations are reversible and differ from the severe burning pain attack lasting 2–7 days. Previously, afamelanotide treatment was studied using time to pain or time outside as primary outcome measures. Since patients have an ingrained fear of sunlight, these measures did not capture the full treatment effect. We retrospectively characterized and evaluated time to prodrome (TTP) as a safer, patient-reported outcome (PRO) measure in afamelanotide-treated patients. Methods: Structured interviews recorded TTP before and during afamelanotide treatment in retrospective US and Dutch cohort studies. Results: Thirty-one US and 58 Dutch EPP patients participated. Before afamelanotide treatment, 54.8% US and 39.7% Dutch patients reported TTP onset

BACKGROUND AND AIMS The risk for hepatocellular carcinoma (HCC) is increased in acute hepatic porphyrias (AHP). The aim of this study was to explore the clinicopathologic characteristics, outcomes, and frequency of HCC in patients with AHP in the United States. APPROACH AND RESULTS This cross-sectional analysis evaluated patients with HCC in a multicenter, longitudinal study of AHP. Among 327 patients with AHP, 5 (1.5%) were diagnosed with HCC. Of the 5 HCC cases, 4 had acute intermittent porphyria and 1 had variegate porphyria, confirmed by biochemical and/or genetic testing. All patients were white females, with a median age of 27 years (range 21-75) at diagnosis. The median age at HCC diagnosis was 69 years (range 61-74). AHP was asymptomatic in 2 patients; 2 reported sporadic attacks; and 1 reported recurrent attacks (>4 attacks/year). All patients had a single HCC lesion on liver imaging that was 1.8-6.5 centimeters in diameter. Serum alpha fetoprotein levels were below 10 ng/mL in all 4 patients with available results. Four patients underwent liver resection, and 1 was treated with radioembolization. No significant inflammation or fibrosis was found in adjacent liver tissues of 3 patients who underwent liver resection. Two patients developed recurrence of HCC at 22 and 26 months following liver resection. All patients are alive with survival times from HCC diagnosis ranging from 26-153 months. CONCLUSION In this U.S. study, 1.5% of patients with AHP had HCC. HCC in AHP occurred in the absence of cirrhosis, which contrasts with other chronic liver diseases. Patients with AHP, regardless of clinical attacks, should be screened for HCC, beginning at age 50. The pathogenesis of hepatocarcinogenesis in AHP is unknown and needs further investigation.

Background 5-Aminolevulinic acid dehydratase (ALAD) porphyria (ADP) is an ultrarare autosomal recessive disease, with only eight documented cases, all of whom were males. Although classified as an acute hepatic porphyria (AHP), induction of the rate limiting hepatic enzyme 5-aminolevulinic acid synthase-1 (ALAS1) has not been demonstrated, and the marrow may also contribute excess 5-aminolevulinic acid (ALA). Two patients have died and reported follow up for the others is limited, so the natural history of this disease is poorly understood and treatment experience limited. Methods We report new molecular findings and update the clinical course and treatment of the sixth reported ADP patient, now 31 years old and the only known case in the Americas, and review published data regarding genotype-phenotype correlation and treatment. Results Circulating hepatic 5-aminolevulinic acid synthase-1 (ALAS1) mRNA was elevated in this case, as in other AHPs. Gain of function mutation of erythroid specific ALAS2 – an X-linked modifying gene in some other porphyrias – was not found. Seven reported ADP cases had compound heterozygous ALAD mutations resulting in very low residual ALAD activity and symptoms early in life or adolescence. One adult with a germline ALAD mutant allele developed ADP in association with a clonal myeloproliferative disorder, polycythemia vera. Conclusions Elevation in circulating hepatic ALAS1 and response to treatment with hemin indicate that the liver is an important source of excess ALA in ADP, although the marrow may also contribute. Intravenous hemin was effective in most reported cases for treatment and prevention of acute attacks of neurological symptoms.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the alpha-galactosidase A (GLA) gene, which encodes the exogalactosyl hydrolase, alpha-galactosidase A (α-Gal A). Deficient α-Gal A activity results in the progressive, systemic accumulation of its substrates, globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), leading to renal, cardiac, and/or cerebrovascular disease and early demise. The current standard treatment for Fabry disease is enzyme replacement therapy, which necessitates lifelong biweekly infusions of recombinant enzyme. A more long-lasting treatment would benefit Fabry patients. Here, a gene therapy approach using an episomal adeno-associated viral 2/6 (AAV2/6) vector that encodes the human GLA cDNA driven by a liver-specific expression cassette was evaluated in a Fabry mouse model that lacks α-Gal A activity and progressively accumulates Gb3 and Lyso-Gb3 in plasma and tissues. A detailed 3-month pharmacology and toxicology study showed that administration of a clinical-scale-manufactured AAV2/6 vector resulted in markedly increased plasma and tissue α-Gal A activities, and essentially normalized Gb3 and Lyso-Gb3 at key sites of pathology. Further optimization of vector design identified the clinical lead vector, ST-920, which produced several-fold higher plasma and tissue α-Gal A activity levels with a good safety profile. Together, these studies provide the basis for the clinical development of ST-920., Graphical Abstract

Background Fabry disease is a rare, X-linked genetic disorder that, if untreated in patients with the Classic phenotype, often progresses to end-stage kidney disease. This meta-analysis determined the effect of agalsidase beta on loss of estimated glomerular filtration rate (eGFR) in the Classic phenotype using an expansive evidence base of individual patient-level data. Methods The evidence base included four Sanofi-Genzyme studies and six studies from a systematic literature review. These were restricted to Classic Fabry patients meeting the eligibility criteria from Phases III and IV agalsidase beta trials, including 315 patients (161 treated). Linear regression was first used to model annual change in eGFR for each patient and the resulting annualized eGFR slopes were modelled with treatment and covariates using quantile regression. These results were then used to estimate median annualized eGFR change in agalsidase beta treated versus untreated groups. Results Imbalances across treatment groups were found in baseline age, sex and proteinuria, but not in the use of renin–angiotensin system blockers. The adjusted model suggests that treated (agalsidase beta) patients experienced a slower median eGFR decrease [2.46 mL/min/1.73 m2/year slower; 95% confidence interval (CI) 0.63–4.29; P = 0.0087] than comparable untreated patients. The median eGFR decrease was 2.64 mL/min/1.73 m2/year slower (95% CI 0.53–4.78; P = 0.0141) in treated Classic males. Conclusions Using an expansive evidence base and robust modelling approach, these data indicate that agalsidase beta-treated patients with the Classic phenotype conserve their renal function better than untreated patients.

Background Porphyrias are a group of rare diseases leading to dysregulation in heme biosynthesis and the accumulation of heme precursors, including porphyrinogens, which in their oxidized states [porphyrins] are reddish or purple. Acute hepatic porphyrias (AHP) comprise four diseases that cause acute debilitating neurovisceral attacks. Despite diagnostic advances, AHP is often undiagnosed or misdiagnosed due to a lack of disease awareness, low clinical suspicion, variable presentation, and nonspecific symptoms that mimic more common diseases. Delays in diagnosis and treatment increase the risk of serious acute and chronic complications. Aim In order to assess whether symptoms alone or in combination might be utilized as important indicators or “purple flags” that, when present, should alert clinicians to suspect AHP and pursue specific diagnostic testing, we conducted a comprehensive review of the literature on AHP, including cohort studies and case reports over two epochs, from 1980 to 2006 and from 2012 to 2018. Results We found that severe abdominal pain, with or without acute central nervous system manifestations and peripheral neuropathy, continues to be recognized the most frequent symptom. Hyponatremia, change in urine color, and certain chronic symptoms were also identified as features that should raise suspicion of AHP. To improve diagnosis of AHP, clinicians need to take a broad perspective, including demographic data and medical history, into consideration. Conclusions The clinical features of AHP continue to be severe pain, especially pain in the abdomen. Other features that should raise suspicion are autonomic, peripheral, or central neuropathies, hyponatremia, and red-purple urine color.

Accumulation of protoporphyrin IX (PPIX) and Zn-PPIX, are the clinical hallmarks of protoporphyria. Phenotypic expression of protoporphyria is due to decreased activity of ferrochelatase (FECH) or to increased activity of aminolevulinic acid synthase (ALAS) in red blood cells. Other genetic defects have been shown to contribute to disease severity including loss of function mutations in the mitochondrial AAA-ATPase, CLPX and mutations in the Iron-responsive element binding protein 2 (IRP2), in mice. It is clear that multiple paths lead to a common phenotype of excess plasma PPIX that causes a phototoxic reaction on sun exposed areas. In this study we examined the association between mitochondrial iron acquisition and utilization with activity of FECH. Our data show that there is a metabolic link between the activity FECH and levels of MFRN1 mRNA. We examined the correlation between FECH activity and MFRN1 mRNA in cell lines established from patients with the classical protoporphyria, porphyria due to defects in ALAS2 mutations. Our data confirm MFRN1 message levels positively correlated with FECH enzymatic activity in all cell types.

Acute Intermittent Porphyria (AIP), an autosomal dominant hepatic disorder, results from hydroxymethylbilane synthase (HMBS) mutations that decrease the encoded enzymatic activity, thereby predisposing patients to life-threatening acute neurovisceral attacks. The ~1% penetrance of AIP suggests that other genetic factors modulate the onset and severity of the acute attacks. Here, we characterized the hepatic transcriptomic response to phenobarbital (PB) administration in AIP mice, which mimics the biochemical attacks of AIP. At baseline, the mRNA profiles of 14,138 hepatic genes prior to treatment were remarkably similar between AIP and the congenic wild-type (WT) mice. After PB treatment (~120mg/kg × 3d), 1,347 and 1,120 genes in AIP mice and 422 and 404 genes in WT mice were uniquely up- and down-regulated, respectively, at a False Discovery Rate 1.9-fold) and Cyp21a1 was upregulated only in PB-induced WT mice (>9-fold). Notably, the genes differentially expressed in induced AIP mice were enriched in circadian rhythm, mitochondria biogenesis and electron transport, suggesting these pathways were involved in AIP mice responding to PB treatment. These results advance our understanding of the hepatic metabolic changes in PB-induced AIP mice and have implications in the pathogenesis of AIP acute attacks.

Author(s): Naik, Hetanshi; Overbey, Jessica R; Desnick, Robert J; Anderson, Karl E; Bissell, D Montgomery; Bloomer, Joseph; Bonkovsky, Herbert L; Phillips, John D; Wang, Bruce; Singal, Ashwani; Balwani, Manisha | Abstract: BackgroundErythropoietic protoporphyria (EPP) and X-linked Protoporphyria (XLP) are rare photodermatoses presenting with severe phototoxicity. Although anecdotally, providers who treat EPP patients acknowledge their life-altering effects, tools that fully capture their impact on quality of life (QoL) are lacking.MethodsAdult patients with EPP/XLP were given four validated QoL tools: the Patient Reported Outcomes Measurement Information System 57 (PROMIS-57), the Hospital Anxiety and Depression Scale (HADS), the Illness Perception Questionnaire Revised (IPQR), and an EPP-Specific tool. All patients received the PROMIS-57 while the HADS, IPQR, and EPP-Specific tools were introduced at a later date. Associations between responses and clinical phenotypes were explored.ResultsTwo hundred and two patients were included; 193 completed PROMIS-57, 104 completed IPQR, 103 completed HADS, and 107 completed the EPP-Specific tool. The IPQR showed that patients strongly believed EPP/XLP had a negative impact on their lives. Mean scores in anxiety and depression domains of both HADS and PROMIS-57 were normal; however, anxiety scores from HADS were borderline/abnormal in 20% of patients. The EPP-Specific tool revealed a decreased QoL in most patients. The PROMIS-57 showed that 21.8% of patients have clinically significant pain interference. Several tool domains correlated with measures of disease severity, most being from the PROMIS-57.ConclusionsImpaired QoL is an important consequence of EPP/XLP. PROMIS-57 was most sensitive in evaluating impaired QoL in EPP/XLP. Further research is needed to compare the effectiveness of it for assessing response to treatment.

BACKGROUND AND AIMS: Acute intermittent porphyria (AIP) results from a partial deficiency of porphobilinogen deaminase (PBGD). Symptomatic AIP patients, most of whom are women, experience acute attacks characterized by severe abdominal pain and abrupt increases in blood pressure. Here, we characterized the reactivity of mesenteric arteries from male and female AIP mice with ~30% of normal PBGD activity and wild type C57BL/6 mice. METHODS: An acute porphyric attack was induced in AIP mice by treatment with phenobarbital. Vascular responses to K(+), phenylephrine (PE), acetylcholine (ACh), and hemin were determined (Wire Multi Myograph). RESULTS: Maximal contraction to PE was increased in arteries from male and female AIP mice (p

Erythropoietic protoporphyria (EPP), the most common porphyria of childhood and the third most common porphyria of adulthood, is characterized clinically by painful, non-blistering cutaneous photosensitivity. Two distinct inheritance patterns involving mutations affecting genes that encode enzymes of the heme biosynthetic pathway underlie the clinical phenotype. Aminolevulinic acid synthase 2 (ALAS2), the rate limiting enzyme of the heme pathway in the erythron, is a therapeutic target in EPP because inhibiting enzyme function would reduce downstream production of protoporphyrin IX (PPIX), preventing accumulation of the toxic molecule and thereby ameliorating symptoms. Isoniazid (INH) is widely used for treatment of latent and active M. tuberculosis (TB). Sideroblastic anemia is observed in some patients taking INH, and studies have shown that this process is a consequence of inhibition of ALAS2 by INH. Based on these observations, we postulated that INH might have therapeutic activity in patients with EPP. We challenged this hypothesis in a murine model of EPP and showed that, after 4 weeks of treatment with INH, both plasma PPIX and hepatic PPIX were significantly reduced. Next, we tested the effect of INH on patients with EPP. After eight weeks, no significant difference in plasma or red cell PPIX was observed among the 15 patients enrolled in the study. These results demonstrate that while INH can lower PPIX in an animal model of EPP, the standard dose used to treat TB is insufficient to affect levels in humans.

Mouse models of the human porphyrias have proven useful for investigations of disease pathogenesis and to facilitate the development of new therapeutic approaches. To date, mouse models have been generated for the major porphyrias, with the exception of X-linked protoporphyria (XLP) and the ultra rare 5-aminolevulinic acid dehydratase deficiency porphyria (ADP). Mouse models have been generated for all three autosomal dominant acute hepatic porphyrias, acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). The AIP mice, in particular, provide a useful investigative model as they have been shown to have acute biochemical attacks when induced with the prototypic porphyrinogenic drug, phenobarbital. In addition to providing important insights into the disease pathogenesis of the neurological impairment in AIP, these mice have been valuable for preclinical evaluation of liver-targeted gene therapy and RNAi-mediated approaches. Mice with severe HMBS deficiency, which clinically and biochemically mimic the early-onset homozygous dominant AIP (HD-AIP) patients, have been generated and were used to elucidate the striking phenotypic differences between AIP and HD-AIP. Mice modeling the hepatocutaneous porphyria, porphyria cutanea tarda (PCT), made possible the identification of the iron-dependent inhibitory mechanism of uroporphyrinogen III decarboxylase (UROD) that leads to symptomatic PCT. Mouse models for the two autosomal recessive erythropoietic porphyrias, congenital erythropoietic porphyria (CEP) and erythropoeitic protoporphyria (EPP), recapitulate many of the clinical and biochemical features of the severe human diseases and have been particularly useful for evaluation of bone marrow transplantation and hematopoietic stem cell (HSC)-based gene therapy approaches. The EPP mice have also provided valuable insights into the underlying pathogenesis of EPP-induced liver damage and anemia.

Acute intermittent porphyria (AIP) is an inborn error of heme biosynthesis due to the deficiency of hydroxymethylbilane synthase (HMBS) activity. Human AIP heterozygotes have episodic acute neurovisceral attacks that typically start after puberty, whereas patients with homozygous dominant AIP (HD-AIP) have early-onset chronic neurological impairment, including ataxia and psychomotor retardation. To investigate the dramatically different manifestations, knock-in mice with human HD-AIP missense mutations c.500G>A (p.Arg167Glu) or c.518_519GC>AG (p.Arg173Glu), designated R167Q or R173Q mice, respectively, were generated and compared with the previously established T1/T2 mice with ~30% residual HMBS activity and the heterozygous AIP phenotype. Homozygous R173Q mice were embryonic lethal, while R167Q homozygous mice (R167Q(+/+)) had ~5% of normal HMBS activity, constitutively elevated plasma and urinary 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), profound early-onset ataxia, delayed motor development and markedly impaired rotarod performance. Central nervous system (CNS) histology was grossly intact, but CNS myelination was delayed and overall myelin volume was decreased. Heme concentrations in liver and brain were similar to those of T1/T2 mice. Notably, ALA and PBG concentrations in the cerebral spinal fluid and CNS regions were markedly elevated in R167Q(+/+) mice compared with T1/T2 mice. When the T1/T2 mice were administered phenobarbital, ALA and PBG markedly accumulated in their liver and plasma, but not in the CNS, indicating that ALA and PBG do not readily cross the blood–brain barrier. Taken together, these studies suggest that the severe HD-AIP neurological phenotype results from decreased myelination and the accumulation of locally produced neurotoxic porphyrin precursors within the CNS.

Acute intermittent porphyria (AIP), an autosomal dominant disorder due to the half-normal activity of hydroxymethylbilane synthase (HMBS), is characterized by acute neurovisceral attacks that are precipitated by factors that induce heme biosynthesis. Molecular diagnosis is the most sensitive and specific diagnostic test for AIP, and importantly, it permits the identification of asymptomatic family members for genetic counseling and avoidance of precipitating factors. Here, we report the identification of 40 novel HMBS mutations, including 11 missense, four nonsense, 16 small insertions or deletions, eight consensus splice site mutations, and a complex insertion-deletion mutation in unrelated individuals with AIP. Prokaryotic expression of the missense mutations demonstrated that all mutants had ≤5% of expressed wildtype activity, except for c.1039G>C (p.A347P), which had 51% residual HMBS activity but was markedly thermolabile. Of note, the mutation c.612G>T (p.Q204H) altered the last nucleotide of exon 10, which resulted in an alternative HMBS transcript with an in-frame nine base-pair deletion at the 3'-terminus of exon 10 (encoding protein Q204HΔ3). When expressed, Q204HΔ3 and an in-frame three base-pair deletion (c.639_641delTGC) had no detectable HMBS activity. Western blot analyses and mapping of the missense mutations on the human HMBS crystal structure revealed that mutations near the active site or at the dimerization interface resulted in stably expressed proteins, while most that altered surface residues resulted in unstable proteins, presumably due to improper protein folding. These studies identified novel pathogenic HMBS mutations and expanded the molecular heterogeneity of AIP.

To review the peripheral neurological complications of the acute hepatic porphyrias, as well as the latest advances in their pathophysiology and management. The diagnosis of porphyric neuropathy remains challenging as varying neuropathic patterns are encountered depending on disease stage, including a non-length-dependent distribution pattern. The major pathophysiologic mechanism is δ-aminolevulinic acid (ALA)–induced neurotoxicity. The less restrictive blood-nerve barrier in the autonomic ganglia and myenteric plexus may explain the frequency of dysautonomic manifestations. Recently, a prophylactic small interfering RNA (siRNA)-based therapy that reduces hepatic ALA Synthase-1 mRNA was approved for patients with recurrent neuro-visceral attacks. Neurologists should appreciate the varying patterns of porphyric neuropathy. As with most toxin-induced axonopathies, long-term outcomes depend on early diagnosis and treatment. While the short-term clinical and biochemical benefits of siRNA-based therapy are known, its long-term effects on motor recovery, chronic pain, and dysautonomic manifestations are yet to be determined.

Fabry disease, a lysosomal storage disorder resulting from the deficient activity of α-galactosidase A (α-Gal A), is characterized by cardiac, renal, and/or cerebrovascular disease due to progressive accumulation of the enzyme's substrates, globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3). We report here the preclinical evaluation of liver-targeted in vivo genome editing using zinc-finger nuclease (ZFN) technology to insert the human α-galactosidase A (hGLA) cDNA into the albumin "safe harbor" locus of Fabry mice, thereby generating an albumin-α-Gal A fusion protein. The mature α-Gal A protein is secreted into the circulation for subsequent mannose-6-phosphate receptor-mediated tissue uptake. Donor vector optimization studies showed that replacing the hGLA cDNA signal peptide sequence with that of human iduronate 2-sulfatase (IDS) achieved higher transgene expression. Intravenous adeno-associated virus (AAV) 2/8-mediated co-delivery of the IDS-hGLA donor and ZFNs targeting the albumin locus resulted in continuous, supraphysiological plasma and tissue α-Gal A activities, which essentially normalized Gb3 and Lyso-Gb3 levels in key tissues of pathology. Notably, this was achieved with10% of hepatocytes being edited to express hGLA, occurring mostly via non-homologous end joining (NHEJ) rather than homology-directed repair (HDR). These studies indicate that ZFN-mediated in vivo genome editing has the potential to be an effective one-time therapy for Fabry disease.

Acute hepatic porphyria comprises a group of rare, genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long-term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months prior to the study, patients reported a median (range) of 6 (0-52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a healthcare facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0-37.0]). Elevated levels of hepatic δ-aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ-aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased healthcare utilization. Conclusions: Patients experienced attacks often requiring treatment in a healthcare facility and/or with hemin, as well as chronic symptoms that adversely influence day-to-day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies. This article is protected by copyright. All rights reserved.

Acute intermittent porphyria (AIP) is an autosomal dominant inborn error of heme biosynthesis due to a pathogenic mutation in the Hmbs gene, resulting in half-normal activity of hydroxymethylbilane synthase. Factors that induce hepatic heme biosynthesis induce episodic attacks in heterozygous patients. The clinical presentation of acute attacks involves the signature neurovisceral pain and may include psychiatric symptoms. Here we used a knock-in mouse line that is biallelic for the Hmbs c.500G > A (p.R167Q) mutation with ~ 5% of normal hydroxymethylbilane synthase activity to unravel the consequences of severe HMBS deficiency on affective behavior and brain physiology. Hmbs knock-in mice (KI mice) model the rare homozygous dominant form of AIP and were used as tool to elucidate the hitherto unknown pathophysiology of the behavioral manifestations of the disease and its neural underpinnings. Extensive behavioral analyses revealed a selective depression-like phenotype in Hmbs KI mice; transcriptomic and immunohistochemical analyses demonstrated aberrant myelination. The uncovered compromised mitochondrial function in the hippocampus of knock-in mice and its ensuing neurogenic and neuroplastic deficits lead us to propose a mechanistic role for disrupted mitochondrial energy production in the pathogenesis of the behavioral consequences of severe HMBS deficiency and its neuropathological sequelae in the brain.

PurposeAcute intermittent porphyria (AIP) is a rare inborn error of heme biosynthesis characterized by life-threatening acute attacks. Few studies have assessed quality of life (QoL) in AIP and those that have had small sample sizes and used tools that may not have captured important domains.MethodsBaseline data from the Porphyrias Consortium's Longitudinal Study were obtained for 259 patients, including detailed disease and medical history data, and the following Patient-Reported Outcomes Measurement Information System (PROMIS) scales: anxiety, depression, pain interference, fatigue, sleep disturbance, physical function, and satisfaction with social roles. Relationships between PROMIS scores and clinical and biochemical AIP features were explored.ResultsPROMIS scores were significantly worse than the general population across all domains, except depression. Each domain discriminated well between asymptomatic and symptomatic patients with symptomatic patients having worse scores. Many important clinical variables like symptom frequency were significantly associated with domain scores in univariate analyses, showing responsiveness of the scales, specifically pain interference and fatigue. However, most regression models only explained ~20% of the variability observed in domain scores.ConclusionPain interference and fatigue were the most responsive scales in measuring QoL in this AIP cohort. Future studies should assess whether these scales capture longitudinal disease progression and treatment response.

Two distinct metabolic derangements are included under the eponym “Niemann–Pick disease (NPD)”. The first is due to the deficient activity of the lysosomal enzyme acid sphingomyelinase (ASM). Patients with this disorder [also referred to as ASM-deficient (ASMD) NPD] are broadly classified as having types A, A/B, and B NPD depending on their degree of neurologic involvement. Type A NPD patients, also known as the infantile neurovisceral form, exhibit hepatosplenomegaly in infancy and profound central nervous system (CNS) involvement. They rarely survive beyond 2–3 years of age. Type B patients, also known as the chronic visceral form, have hepatosplenomegaly and pathologic alterations of their lungs, but there are usually no CNS signs. The age of onset and rate of disease progression varies greatly among type B patients, and many may survive into adulthood. Patients with phenotypes intermediate between types A and B NPD (type A/B), also known as the chronic neurovisceral form, also have been identified. These individuals represent the expected continuum caused by inheriting different mutations in the ASM gene (SMPD1). Patients in the second NPD category are designated as having types C and D NPD. These individuals may have mild hepatosplenomegaly, but the CNS is profoundly affected. Impaired intracellular trafficking of cholesterol causes types C and D NPD, and two distinct gene defects have been found. All type D patients originate from a common Nova Scotian ancestry.

Recent research has suggested a possible link between Parkinson's disease (PD) and Fabry disease. To test this relationship, we administered a self-report and family history questionnaire to determine the prevalence of PD in Fabry disease patients and family members with likely pathogenic alpha-galactosidase A (GLA) mutations. A total of 90 Fabry patients (77 from the online survey and 13 from the Icahn School of Medicine at Mount Sinai (ISMMS)) were included in the analysis. Two of the Fabry disease patients who completed the online survey were diagnosed with PD (2/90, 2.2%). Among probands older than 60, 8.3% (2/24) were diagnosed with PD. Using Kaplan Meier survival analysis, the age-specific risk of PD by age 70 was 11.1%. Family history was available on 72 Fabry families from the online study and 9 Fabry families from ISMMS. Among these 81 families, 6 (7.4%) had one first degree relative who fit the criteria for a conservative diagnosis of PD. The results of this study suggest that there may be an increased risk of developing PD in individuals with GLA mutations, but these findings should be interpreted with caution given the limitations of the study design.

BackgroundFabry Disease (FD), an X linked lysosomal storage disease due to pathogenic α-galactosidase A (GLA) mutations, results in two major subtypes, the early-onset Type 1 ‘Classic’ and the Type 2 ‘Later-Onset’ phenotypes. To identify previously unrecognised patients, investigators screened cardiac, renal and stroke clinics by enzyme assays. However, some screening studies did not perform confirmatory GLA mutation analyses, and many included recently recognised ‘benign/likely-benign’ variants, thereby inflating prevalence estimates.MethodsOnline databases were searched for all FD screening studies in high-risk clinics (1995–2017). Studies reporting GLA mutations were re-analysed for pathogenic mutations, sex and phenotype. Phenotype-specific and sex-specific prevalence rates were determined.ResultsOf 67 studies, 63 that screened 51363patients (33943M and 17420F) and provided GLA mutations were reanalysed for disease-causing mutations. Of reported GLA mutations, benign variants occurred in 47.9% of males and 74.1% of females. The following were the revised prevalence estimates: among 36820 (23954M and 12866F) haemodialysis screenees, 0.21% males and 0.15% females; among 3074 (2031M and 1043F) renal transplant screenees, 0.25% males and no females; among 5491 (4054M and 1437F) cardiac screenees, 0.94% males and 0.90% females; and among 5978 (3904M and 2074F) stroke screenees, 0.13% males and 0.14% females. Among male and female screenees with pathogenic mutations, the type 1 Classic phenotype was predominant (~60%), except more male cardiac patients (75%) had type 2 Later-Onset phenotype.ConclusionsCompared with previous findings, reanalysis of 63 studies increased the screenee numbers (~3.4-fold), eliminated 20 benign/likely benign variants, and provided more accurate sex-specific and phenotype-specific prevalence estimates, ranging from ~0.13% of stroke to ~0.9% of cardiac male or female screenees.

The focal facial dermal dysplasias (FFDDs) are a group of rare inherited developmental disorders characterized by congenital scar-like atrophic lesions in the bitemporal (FFDD1, 2, and 3) or preauricular (FFDD4) areas. FFDD4 is an autosomal-recessive trait characterized by preauricular skin defects without additional dysmorphic findings. Previously, only two CYP26C1 mutations in four unrelated patients with FFDD4 were reported. Here, we report two additional unrelated FFDD4 patients with four CYP26C1 mutations including three novel lesions: a missense mutation, c.230G>C (p.Arg77Pro), and two splice-site mutations, c.1191+1G>T (IVS5(+1)G>T) and c.1191+2insT (IVS5(+2)insT). In silico analyses predicted all three mutations as pathogenic. Compound heterozygosity was validated through parental studies. These results provide further evidence that CYP26C1 mutations are the molecular genetic basis of FFDD4. Identification of additional cases by dermatologists, pediatricians, and medical geneticists will lead to further understanding of the clinical spectrum of FFDD4 and define its molecular genetic heterogeneity.

Fabry disease, an X-linked lysosomal storage disease, results from deficient α-galactosidase A (α-GalA) activity and the systemic accumulation of α-galactosyl-terminated glycosphingolipids. Two major phenotypes, "Classic" and "Later-Onset", lead to renal failure, and/or cardiac disease, and early demise. To date, the evolution and progression of the cardiac pathology and resultant clinical manifestations in family members of phenotype have not been well characterized.In a Classic family with nine affected members (GLA mutation c.983delG), cardiac imaging, angiography, and cardiac biopsies were performed in four males and two heterozygous females. Tissues were examined histologically, ultrastructurally, and myocardial necrosis and apoptosis were evaluated by in situ ligation with hairpin probes. Increasing cardiac pathology correlated with ECG and cardiac magnetic resonance findings. Young affected males with "pre-hypertrophy" had 18-20μm cardiomyocyte diameters,30% vacuolar areas in myocytes, and normal levels of necrosis and apoptosis. Patients with "moderate hypertrophy" (maximal wall thickness (MWT) ≤16mm) had 30-35μm cardiomyocyte diameters, ~45% vacuolar areas, and moderate levels of necrosis and apoptosis. In contrast, the oldest male with severe hypertrophy (MWT=21mm) had 38-40μm cell diameters,60% vacuolar areas, and marked necrosis and apoptosis.Progressive gender-specific cardiac pathology and clinical manifestations were documented in affected Classic family members. Increasing cardiomyocyte diameter was correlated with disease severity, age, and gender. Fibrosis was presumably caused by cell death of enlarged, substrate-engorged cardiomyocytes. These results support early enzyme therapy in Classic males to prevent/minimize irreversible cardiac damage.

Focal facial dermal dysplasias (FFDDs) are rare genetic/developmental disorders characterised by bilateral 'scar-like' facial lesions. Four subtypes are classified by the bitemporal (FFDD1-3) or preauricular (FFDD4) lesion location. FFDD1-3 are differentiated by additional facial abnormalities and inheritance patterns. Although the genetic defects causing FFDD1 and FFDD2 remain unknown, recent studies identified defects causing FFDD3 and FFDD4. Here, the clinical phenotypes, genetic defects and inheritance of the four FFDD subtypes are described. In addition, the overlapping facial abnormalities in FFDD3 and two other genetic disorders, Ablepharon macrostomia syndrome and Barber-Say syndrome, are noted. Familiarity with the FFDDs by clinicians will further delineate the phenotypes and genetic/developmental defects of these dermal facial disorders.

Purpose: Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene. Migalastat, a pharmacological chaperone, binds to specific mutant forms of α-galactosidase A to restore lysosomal activity. Methods: A pharmacogenetic assay was used to identify the α-galactosidase A mutant forms amenable to migalastat. Six hundred Fabry disease–causing mutations were expressed in HEK-293 (HEK) cells; increases in α-galactosidase A activity were measured by a good laboratory practice (GLP)-validated assay (GLP HEK/Migalastat Amenability Assay). The predictive value of the assay was assessed based on pharmacodynamic responses to migalastat in phase II and III clinical studies. Results: Comparison of the GLP HEK assay results in in vivo white blood cell α-galactosidase A responses to migalastat in male patients showed high sensitivity, specificity, and positive and negative predictive values (≥0.875). GLP HEK assay results were also predictive of decreases in kidney globotriaosylceramide in males and plasma globotriaosylsphingosine in males and females. The clinical study subset of amenable mutations (n = 51) was representative of all 268 amenable mutations identified by the GLP HEK assay. Conclusion: The GLP HEK assay is a clinically validated method of identifying male and female Fabry patients for treatment with migalastat. Genet Med 19 4, 430–438.

The eponym Niemann-Pick disease (NPD) refers to a group of patients who present with varying degrees of lipid storage and foam cell infiltration in tissues, as well as overlapping clinical features including hepatosplenomegaly, pulmonary insufficiency and/or central nervous system (CNS) involvement. Due to the pioneering work of Roscoe Brady and co-workers, we now know that there are two distinct metabolic abnormalities that account for NPD. The first is due to the deficient activity of the enzyme acid sphingomyelinase (ASM; “types A & B” NPD), and the second is due to defective function in cholesterol transport (“type C” NPD). Herein only types A and B NPD will be discussed. Type A NPD patients exhibit hepatosplenomegaly in infancy and profound CNS involvement. They rarely survive beyond 2–3 years of age. Type B patients also have hepatosplenomegaly and pathologic alterations of their lungs, but there are usually no CNS signs. The age of onset and rate of disease progression varies greatly among type B patients, and they frequently live into adulthood. Intermediate patients also have been reported with mild to moderate neurological findings. All patients with types A and B NPD have mutations in the gene encoding ASM (SMPD1), and thus the disease is more accurately referred to as ASM deficiency (ASMD). Herein we will review the clinical, pathological, biochemical, and genetic findings in types A and B NPD, and emphasize the seminal contributions of Dr. Brady to this disease. We will also discuss the current status of therapy for this disorder.

Acute Intermittent Porphyria (AIP), an autosomal dominant inborn error of heme metabolism, typically presents in adulthood, most often in women in the reproductive age group. There are limited reports on the clinical presentation in children, and in contrast to the adults, most of the reported pediatric cases are male. While acute abdominal pain is the most common presenting symptom in children, seizures are commonly seen and may precede the diagnosis of AIP. As an example, we report a 9 year old developmentally normal pre-pubertal boy who presented with acute abdominal pain, vomiting and constipation followed by hyponatremia, seizures, weakness and neuropathy. After a diagnostic odyssey, his urine porphobilinogen was found to be significantly elevated and genetic testing showed a previously unreported consensus splice-site mutation IVS4-1G>A in the HMBS gene confirming the diagnosis of AIP. Here, we discuss the clinical presentation in this case, and 15 reported pediatric cases since the last review 30 years ago and discuss the differential diagnosis and challenges in making the diagnosis in children. We review the childhood-onset cases reported in the Longitudinal Study of the Porphyrias Consortium. Of these, genetically and biochemically confirmed patients, 11 of 204 (5%) reported onset of attacks in childhood. Most of these patients (91%) reported recurrent attacks following the initial presentation. Thus, AIP should be considered in the differential diagnosis of children presenting with unexplained abdominal pain, seizures, weakness and neuropathy.

Background Recently, several studies revealed a much higher prevalence of later onset Fabry disease (FD) than previously expected. It suggested that later onset FD might present as an important hidden health issue in certain ethnic or demographic populations in the world. However, the natural history of its phenotype has not been systemically investigated, especially the cardiac involvement. Objectives The study analyzed a large-scale newborn screening program for FD to understand the natural course of later onset FD. Methods To date, 916,383 newborns have been screened for FD in Taiwan, including more than 1,200 individuals with the common, later onset IVS4+919G>A (IVS4) mutation. Echocardiography was performed in 620 adults with the IVS4 mutation to analyze the prevalence of left ventricular hypertrophy (LVH), and gadolinium-enhanced cardiac magnetic resonance imaging was performed in 129 patients with FD, including 100 IVS4 adults. Results LVH was observed in 67% of men and 32% of women older than 40 years. Imaging evidenced significant late gadolinium enhancement in 38.1% of IVS4 men and 16.7% of IVS4 women with the IVS4 mutation but without LVH. Seventeen patients underwent endomyocardial biopsies, which revealed significant globotriaosylceramide substrate accumulation in their cardiomyocytes. Conclusions Significant cardiomyocyte substrate accumulation in IVS4 patients led to severe and irreversible cardiac fibrosis before development of LVH or other significant cardiac manifestations. Thus, it might be too late to start enzyme replacement therapy after the occurrence of LVH or other significant cardiac manifestations in patients with later onset FD. This study also indicated the importance of newborn screening for early detection of the insidious, ongoing, irreversible cardiac damage in patients with later onset FD.

With the advent of precision and genomic medicine, a critical issue is whether a disease gene variant is pathogenic or benign. Such is the case for the three autosomal dominant acute hepatic porphyrias (AHPs), including acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria, each resulting from the half-normal enzymatic activities of hydroxymethylbilane synthase, coproporphyrinogen oxidase, and protoporphyrinogen oxidase, respectively. To date, there is no public database that documents the likely pathogenicity of variants causing the porphyrias, and more specifically, the AHPs with biochemically and clinically verified information. Therefore, an international collaborative with the European Porphyria Network and the National Institutes of Health/National Center for Advancing Translational Sciences/National Institute of Diabetes and Digestive and Kidney Diseases (NIH/NCATS/NIDDK)-sponsored Porphyrias Consortium of porphyria diagnostic experts is establishing an online database that will collate biochemical and clinical evidence verifying the pathogenicity of the published and newly identified variants in the AHP-causing genes. The overall goal of the International Porphyria Molecular Diagnostic Collaborative is to determine the pathogenic and benign variants for all eight porphyrias. Here we describe the overall objectives and the initial efforts to validate pathogenic and benign variants in the respective heme biosynthetic genes causing the AHPs.

Congenital erythropoietic porphyria (CEP) is a rare autosomal recessive disorder characterized by photosensitivity and by hematologic abnormalities in affected individuals. CEP is caused by mutations in the uroporphyrinogen synthase (UROS) gene. In three reported cases, CEP has been associated with a specific X-linked GATA1 mutation. Disease-causing mutations in either gene result in absent or markedly reduced UROS enzymatic activity. This in turn leads to the accumulation of the non-physiologic and photoreactive porphyrinogens, uroporphyrinogen I and coproporphyrinogen I, which damage erythrocytes and elicit a phototoxic reaction upon light exposure. The clinical spectrum of CEP depends on the level of residual UROS activity, which is determined by the underlying pathogenic loss-of-function UROS mutations. Disease severity ranges from non-immune hydrops fetalis in utero to late-onset disease with only mild cutaneous involvement. The clinical characteristics of CEP include exquisite photosensitivity to visible light resulting in bullous vesicular lesions which, when infected lead to progressive photomutilation of sun-exposed areas such as the face and hands. In addition, patients have erythrodontia (brownish discoloration of teeth) and can develop corneal scarring. Chronic transfusion-dependent hemolytic anemia is common and leads to bone marrow hyperplasia, which further increases porphyrin production. Management of CEP consists of strict avoidance of exposure to visible light with sun-protective clothing, sunglasses, and car and home window filters. Adequate care of ruptured vesicles and use of topical antibiotics is indicated to prevent superinfections and osteolysis. In patients with symptomatic hemolytic anemia, frequent erythrocyte cell transfusions may be necessary to suppress hematopoiesis and decrease marrow production of the phototoxic porphyrins. In severe transfection-dependent cases, bone marrow or hematopoietic stem cell transplantation has been performed, which is curative. Therapeutic approaches including gene therapy, proteasome inhibition, and pharmacologic chaperones are under investigation.

Background The acute hepatic porphyrias (AHPs) are rare inborn errors of heme biosynthesis, characterized clinically by life-threatening acute neurovisceral attacks. Patients with recurrent attacks have a decreased quality of life (QoL); however, no interactive assessment of these patients' views has been reported. We conducted guided discussions regarding specific topics, to explore patients' disease experience and its impact on their lives. Methods Sixteen AHP patients experiencing acute attacks were recruited to moderator-led online focus groups. Five groups (3–4 patients each) were conducted and thematic analyses to identify, examine, and categorize patterns in the data was performed. Results All patients identified prodromal symptoms that began days prior to acute severe pain; the most common included confusion (“brain fog"), irritability, and fatigue. Patients avoided hospitalization due to prior poor experiences with physician knowledge of AHPs or their treatment. All patients used complementary and alternative medicine treatments to avoid hospitalization or manage chronic pain and 81% reported varying degrees of effectiveness. All patients indicated their disease impacted personal relationships due to feelings of isolation and difficulty adjusting to the disease's limitations. Conclusion Patients with recurrent attacks recognize prodromal warning symptoms, attempt to avoid hospitalization, turn to alternative treatments, and have markedly impaired QoL. Counseling and individualized support is crucial for AHP patients with recurrent attacks.

Acute intermittent porphyria results from hydroxymethylbilane synthase (HMBS) mutations that markedly decrease HMBS enzymatic activity. This dominant disease is diagnosed when heterozygotes have life-threatening acute attacks, while most heterozygotes remain asymptomatic and undiagnosed. Although >400 HMBS mutations have been reported, the prevalence of pathogenic HMBS mutations in genomic/exomic databases, and the actual disease penetrance are unknown. Thus, we interrogated genomic/exomic databases, identified non-synonymous variants (NSVs) and consensus splice-site variants (CSSVs) in various demographic/racial groups, and determined the NSV's pathogenicity by prediction algorithms and in vitro expression assays. Caucasians had the most: 58 NSVs and two CSSVs among ∼92,000 alleles, a 0.00575 combined allele frequency. In silico algorithms predicted 14 out of 58 NSVs as "likely-pathogenic." In vitro expression identified 10 out of 58 NSVs as likely-pathogenic (seven predicted in silico), which together with two CSSVs had a combined allele frequency of 0.00056. Notably, six presumably pathogenic mutations/NSVs in the Human Gene Mutation Database were benign. Compared with the recent prevalence estimate of symptomatic European heterozygotes (∼0.000005), the prevalence of likely-pathogenic HMBS mutations among Caucasians was >100 times more frequent. Thus, the estimated penetrance of acute attacks was ∼1% of heterozygotes with likely-pathogenic mutations, highlighting the importance of predisposing/protective genes and environmental modifiers that precipitate/prevent the attacks.

BACKGROUNDLaboratory diagnosis of erythropoietic protoporphyria (EPP) requires a marked increase in total erythrocyte protoporphyrin (300–5000 μg/dL erythrocytes, reference interval CONTENTIn studying more than 180 patients with EPP and XLP, the Porphyrias Consortium found that erythrocyte protoporphyrin concentrations for some patients were much higher (4.3- to 46.7-fold) than indicated by previous reports provided by these patients. The discrepant earlier reports, which sometimes caused the diagnosis to be missed initially, were from laboratories that measure protoporphyrin only by hematofluorometry, which is intended primarily to screen for lead poisoning. However, the instrument can calculate results on the basis of assumed hematocrits and reports results as “free” and “zinc” protoporphyrin (with different reference intervals), implying separate measurements of metal-free and zinc protoporphyrin. Such misleading reports impair diagnosis and monitoring of patients with protoporphyria.SUMMARYWe suggest that laboratories should prioritize testing for EPP and XLP, because accurate measurement of erythrocyte total and metal-free protoporphyrin is essential for diagnosis and monitoring of these conditions, but less important for other disorders. Terms and abbreviations used in reporting erythrocyte protoporphyrin results should be accurately defined.

Introduction Erythropoietic Protoporphyria (EPP) or X-Linked Protoporphyria (XLP) are inborn errors of heme biosynthesis caused by the abnormal accumulation of erythrocyte protoporphyrin IX (ePPIX). These protoporphyrias are characterized by excruciating painful attacks on prolonged sunlight exposure. Before the onset of phototoxic pain, patients experience characteristic prodromal symptoms which serves as a warning signal to avoid further sun exposure. Of note, patients with higher ePPIX levels report shorter times to symptoms compared to patients with lower median ePPIX levels (JAMA Derm, 2017; 153). Here we report the safety and effectiveness of Dersimelagon (MT-7117), a novel, orally-administered, small molecule, selective melanocortin-1 receptor (MC1R) agonist that increases skin melanin without sun exposure and is being developed to increase light tolerance in EPP/XLP patients. Results of the primary, secondary efficacy endpoints, and post-hoc subgroup analyses evaluating effects of baseline ePPIX levels on treatment response will be presented. Methods The MT-7117-A01 (ENDEAVOR) study was a Phase 2, multi-center, randomized, placebo-controlled study with a 16-week double-blind treatment period. A total of 102 EPP/XLP patients were randomized to 3 groups: placebo once daily (QD) (n=35 [31 EPP/4 XLP]), MT-7117 100 mg QD (n=33 [31 EPP/2 XLP]), and MT-7117 300 mg QD (n=34 [31 EPP/3 XLP]). Results of the primary endpoint, increase in the average daily time (min) to first prodromal symptom during sunlight exposure, and secondary endpoints including 1) average daily duration of sunlight exposure without prodromal symptoms, 2) total number of sunlight exposure episodes with prodromal symptoms, and 3) total number of pain events, and post-hoc subgroup analyses evaluating baseline median ePPIX levels are presented here. Safety and tolerability were also assessed. Results There was a significant improvement in average daily time (>50 min) to first prodromal symptom [the primary endpoint] associated with sunlight exposure in subjects treated with MT-7117 100 mg (p=0.008) or 300 mg (p=0.003) compared to placebo at Week 16. Multiple secondary endpoints supported primary endpoint. There was a significant increase in average daily minutes of sunlight exposure without prodromal symptoms at Week 16 in 100 mg (p=0.009) and 300 mg (p=0.004) treated subjects compared to placebo, with an increased average exposure time without prodromal symptoms of ~50 min in MT-7117 subjects at both doses compared to placebo. There was also a 40% reduction in the total number of sunlight exposure episodes with prodromal symptoms in 100 mg (p=0.019) and 300 mg (p=0.006) subjects compared to placebo. There was a significant decrease in the total number of pain events reported in 100 mg (p=0.027, 60% reduction) and 300 mg (p=0.028, 50% reduction) subjects compared to placebo. The post-hoc subgroup analysis evaluating the effects of baseline ePPIX levels in subjects grouped based on the baseline median ePPIX level of 1981 µg/dL. There was a statistically significant increase in average daily time to first prodromal symptom in the subgroup with ePPIX levels ≥1981 µg/dL receiving 100 mg (p=0.020) and 300 mg (p=0.003) compared to placebo. A trend to beneficial effect was also observed for the subgroup of subjects with ePPIX levels MT-7117 had an acceptable safety and tolerability profile. The most common treatment-related treatment emergent adverse reactions were nausea (27.9%), ephelides (23.5%), and skin hyperpigmentation (20.6%). Conclusion The results of the primary efficacy endpoint and multiple secondary endpoints in this Phase 2 study indicate that the oral, MC1R agonist dersimelagon was efficacious after 16 weeks of treatment in increasing symptom-free light exposure in patients with EPP or XLP at doses of 100 and 300 mg QD and showed an acceptable safety and tolerability profile. The post-hoc analyses showed more profound and statistically significant efficacy at both doses for the subgroup with higher baseline median ePPIX levels. Disclosures Balwani: Alnylam Pharmaceuticals: Consultancy, Honoraria, Research Funding; Recordati Rare Diseases: Consultancy, Honoraria, Other: Disease information video recording. Anderson:Alnylam Pahrmaceuticals: Consultancy; Recordati Rare Diseases: Consultancy; Mitsubishi Tanabe Pharma: Consultancy.

The inborn errors of heme biosynthesis, the Porphyrias, include eight major disorders resulting from loss-of-function (LOF) or gain-of-function (GOF) mutations in eight of the nine heme biosynthetic genes. The major sites of heme biosynthesis are the liver and erythron, and the underlying pathophysiology of each of these disorders depends on the unique biochemistry, cell biology, and genetic mechanisms in these tissues. The porphyrias are classified into three major categories: 1) the acute hepatic porphyrias (AHPs), including Acute Intermittent Porphyria (AIP), Hereditary Coproporphyria (HCP), Variegate Porphyria (VP), and 5-Aminolevlulinic Acid Dehydratase Deficient Porphyria (ADP); 2) a hepatic cutaneous porphyria, Porphyria Cutanea Tarda (PCT); and 3) the cutaneous erythropoietic porphyrias, Congenital Erythropoietic Porphyria (CEP), Erythropoietic Protoporphyria (EPP), and X-Linked Protoporphyria (XLP). Their modes of inheritance include autosomal dominant with markedly decreased penetrance (AIP, VP, and HCP), autosomal recessive (ADP, CEP, and EPP), or X-linked (XLP), as well as an acquired sporadic form (PCT). There are severe homozygous dominant forms of the three AHPs. For each porphyria, its phenotype, inheritance pattern, unique genetic principles, and molecular genetic heterogeneity are presented. To date, >1000 mutations in the heme biosynthetic genes causing their respective porphyrias have been reported, including low expression alleles and genotype/phenotype correlations that predict severity for certain porphyrias. The tissue-specific regulation of heme biosynthesis and the unique genetic mechanisms for each porphyria are highlighted.

Porphyria Cutanea Tarda (PCT) is a cutaneous porphyria that results from the hepatic inhibition of the heme biosynthetic enzyme uroporphyrinogen decarboxylase (UROD), and can occur either in the absence or presence of an inherited heterozygous UROD mutation (PCT subtypes 1 and 2, respectively). A heterozygous UROD mutation causes half-normal levels of UROD activity systemically, which is a susceptibility factor but is not sufficient alone to cause type 2 PCT. In both Types 1 and 2 PCT, the cutaneous manifestations are precipitated by additional factors that lead to generation of an inhibitor that more profoundly reduces hepatic UROD activity. PCT is an iron-related disorder, and many of its known susceptibility factors, which include infections (e.g. hepatitis C virus, HIV), high alcohol consumption, smoking, estrogens, and genetic traits (e.g. hemochromatosis mutations) can increase hepatic iron accumulation. Hepatoerythropoietic Porphyria (HEP) is a rare autosomal recessive disease that results from homozygosity or compound heterozygosity for UROD mutations and often causes infantile or childhood onset of both erythropoietic and cutaneous manifestations. During the 11-year period from 01/01/2007 through 12/31/2017, the Mount Sinai Porphyrias Diagnostic Laboratory provided molecular diagnostic testing for 387 unrelated patients with PCT and four unrelated patients with HEP. Of the 387 unrelated individuals tested for Type 2 PCT, 79 (20%) were heterozygous for UROD mutations. Among 26 family members of mutation-positive PCT patients, eight (31%) had the respective family mutation. Additionally, of the four unrelated HEP patients referred for UROD mutation analyses, all had homozygosity or compound heterozygosity for UROD mutations, and all eight asymptomatic family members were heterozygotes for UROD mutations. Of the UROD mutations identified, 19 were novel, including nine missense, two nonsense, one consensus splice-site, and seven insertions and deletions. These results expand the molecular heterogeneity of PCT and HEP by adding a total of 19 novel UROD mutations. Moreover, the results document the usefulness of molecular testing to confirm a genetic susceptibility trait in Type 2 PCT, confirm a diagnosis in HEP, and identify heterozygous family members.

BACKGROUND Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene that obliterate or markedly reduce α-galactosidase A activity. This results in the systemic accumulation of its glycosphingolipid substrates in body fluids and organs, including the kidney. Fabry nephropathy can lead to end-stage renal disease requiring kidney transplantation. Little is known about its long-term outcomes and the overall patient survival after kidney transplantation. METHODS Here, we report 17 Fabry patients (15 male and 2 female subjects) who received kidney transplants and their long-term treatment and follow-up at 4 specialized Fabry centers. RESULTS The posttransplant follow-up ranged to 25 years, with a median of 11.5 (range, 0.8-25.5] years. Graft survival was similar, and death-censored graft survival was superior to matched controls. Fabry patients died with functioning kidneys, mostly from cardiac causes. In 2 male subjects 14 and 23 years posttransplant, the grafts had a few typical FD lamellar inclusions, presumably originating from invading host macrophages and vascular endothelial cells. CONCLUSIONS We conclude that kidney transplantation has an excellent long-term outcome in FD.

Background X-linked protoporphyria (XLP) (MIM 300752) is an erythropoietic porphyria due to gain-of-function mutations in the last exon (Ducamp et al., Hum Mol Genet 22:1280-88, 2013) of the erythroid-specific aminolevulinate synthase gene (ALAS2). Five ALAS2 exon 11 variants identified by the NHBLI Exome sequencing project (p.R559H, p.E565D, p.R572C, p.S573F and p.Y586F) were expressed, purified and characterized in order to assess their possible contribution to XLP. To further characterize the XLP gain-of-function region, five novel ALAS2 truncation mutations (p.P561X, p.V562X, p.H563X, p.E569X and p.F575X) were also expressed and studied. Methods Site-directed mutagenesis was used to generate ALAS2 mutant clones and all were prokaryotically expressed, purified to near homogeneity and characterized by protein and enzyme kinetic assays. Standard deviations were calculated for 3 or more assay replicates. Results The five ALAS2 single nucleotide variants had from 1.3- to 1.9-fold increases in succinyl-CoA Vmax and 2- to 3-fold increases in thermostability suggesting that most could be gain-of-function modifiers of porphyria instead of causes. One SNP (p.R559H) had markedly low purification yield indicating enzyme instability as the likely cause for XLSA in an elderly patient with x-linked sideroblastic anemia. The five novel ALAS2 truncation mutations had increased Vmax values for both succinyl-CoA and glycine substrates (1.4 to 5.6-fold over wild-type), while the Kms for both substrates were only modestly changed. Of interest, the thermostabilities of the truncated ALAS2 mutants were significantly lower than wild-type, with an inverse relationship to Vmax fold-increase. Conclusions Patients with porphyrias should always be assessed for the presence of the ALAS2 gain-of-function modifier variants identified here. A key region of the ALAS2 carboxyterminal region is identified by the truncation mutations studied here and the correlation of increased thermolability with activity suggests that increased molecular flexibility/active site openness is the mechanism of enhanced function of mutations in this region providing further insights into the role of the carboxyl-terminal region of ALAS2 in the regulation of erythroid heme synthesis. Electronic supplementary material The online version of this article (10.1186/s10020-019-0070-9) contains supplementary material, which is available to authorized users.

The acute hepatic porphyrias (AHPs) are inborn errors of heme biosynthesis, which include three autosomal dominant porphyrias, Acute Intermittent Porphyria (AIP), Hereditary Coproporphyria (HCP), and Variegate Porphyria (VP), and the ultra-rare autosomal recessive porphyria, δ-Aminolevulinic Acid Dehydratase Deficiency Porphyria (ADP). AIP, HCP, VP, and ADP each results from loss-of-function (LOF) mutations in their disease-causing genes: hydroxymethylbilane synthase (HMBS); coproporphyrinogen oxidase (CPOX); protoporphyrinogen oxidase (PPOX), and δ-aminolevulinic acid dehydratase (ALAD), respectively. During the 11-year period from January 1, 2007 through December 31, 2017, the Mount Sinai Porphyrias Diagnostic Laboratory diagnosed 315 unrelated AIP individuals with HMBS mutations, including 46 previously unreported mutations, 29 unrelated HCP individuals with CPOX mutations, including 11 previously unreported mutations, and 54 unrelated VP individuals with PPOX mutations, including 20 previously unreported mutations. Overall, of the 1692 unrelated individuals referred for AHP molecular diagnostic testing, 398 (23.5%) had an AHP mutation. Of the 650 family members of mutation-positive individuals tested for an autosomal dominant AHP, 304 (46.8%) had their respective family mutation. These data expand the molecular genetic heterogeneity of the AHPs and document the usefulness of molecular testing to confirm the positive biochemical findings in symptomatic patients and identify at-risk asymptomatic family members.

The erythropoietic porphyrias are inborn errors of heme biosynthesis with prominent cutaneous manifestations. They include autosomal recessive Congenital Erythropoietic Porphyria (CEP) due to loss-of-function (LOF) mutations in the Uroporphyrinogen III Synthase (UROS) gene, Erythropoietic Protoporphyria (EPP) due to LOF mutations in the ferrochelatase (FECH) gene, and X-Linked Protoporphyria (XLP) due to gain-of-function mutations in the terminal exon of the Aminolevulinic Acid Synthase 2 (ALAS2) gene. During the 11-year period from 01/01/2007 through 12/31/2017, the Mount Sinai Porphyrias Diagnostic Laboratory provided molecular diagnostic testing for one or more of these disorders in 628 individuals, including 413 unrelated individuals. Of these 628, 120 patients were tested for CEP, 483 for EPP, and 331 for XLP, for a total of 934 tests. For CEP, 24 of 78 (31%) unrelated individuals tested had UROS mutations, including seven novel mutations. For EPP, 239 of 362 (66%) unrelated individuals tested had pathogenic FECH mutations, including twenty novel mutations. The IVS3-48 T > C low-expression allele was present in 231 (97%) of 239 mutation-positive EPP probands with a pathogenic FECH mutation. In the remaining 3%, three patients with two different FECH mutations in trans were identified. For XLP, 24 of 250 (10%) unrelated individuals tested had ALAS2 exon 11 mutations. No novel ALAS2 mutations were identified. Among family members referred for testing, 33 of 42 (79%) CEP, 62 of 121 (51%) EPP, and 31 of 81 (38%) XLP family members had the respective family mutation. Mutation-positive CEP, EPP, and XLP patients who had been biochemically tested had marked elevations of the disease-appropriate porphyrin intermediates. These results expand the molecular heterogeneity of the erythropoietic porphyrias by adding a total of 27 novel mutations. The results document the usefulness of molecular testing to confirm the positive biochemical findings in these patients and to identify heterozygous family members.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene leading to deficient α-galactosidase A activity, glycosphingolipid accumulation, and life-threatening complications. Phenotypes vary from the "classic" phenotype, with pediatric onset and multi-organ involvement, to later-onset, a predominantly cardiac phenotype. Manifestations are diverse in female patients in part due to variations in residual enzyme activity and X chromosome inactivation patterns. Enzyme replacement therapy (ERT) and adjunctive treatments can provide significant clinical benefit. However, much of the current literature reports outcomes after late initiation of ERT, once substantial organ damage has already occurred. Updated monitoring and treatment guidelines for pediatric patients with Fabry disease have recently been published. Expert physician panels were convened to develop updated, specific guidelines for adult patients. Management of adult patients depends on 1) a personalized approach to care, reflecting the natural history of the specific disease phenotype; 2) comprehensive evaluation of disease involvement prior to ERT initiation; 3) early ERT initiation; 4) thorough routine monitoring for evidence of organ involvement in non-classic asymptomatic patients and response to therapy in treated patients; 5) use of adjuvant treatments for specific disease manifestations; and 6) management by an experienced multidisciplinary team.

Setleis syndrome, focal facial dermal dysplasia type III (FFDD3, MIM #227260), is characterized by scar-like bitemporal lesions and other ocular and facial dysmorphic features. The syndrome results from recessive mutations in the TWIST2 gene, encoding a basic helix-loop-helix transcription factor or de novo genomic duplication or triplication, which include 1.3 Mb at 1p36.22p36.21, or other yet undefined lesions, emphasizing the syndrome's genetic heterogeneity. Recently, three patients were reported with 1p36.22p36.21 duplications/triplication that had the characteristic FFDD3 features and developmental delay or intellectual disabilities. Here, we describe a male with this microduplication, and the typical FFDD3 phenotype, but normal intelligence. Notably, his duplication was inherited from his father who did not have any FFDD3 manifestations, indicating lack of penetrance of the 1p36.22p36.21 microduplication. These findings emphasize phenotypic heterogeneity of the 1p36.22p36.21 copy number variant and the importance of screening the parents of patients with the 1p36.22p36.21 copy number variant to determine whether the duplication/triplication is de novo or inherited, for informed reproductive and genetic counseling.

Fabry disease is an X-linked lysosomal storage disease caused by deficient activity of α-galactosidase A and the resultant systemic accumulation of globotrioasylceramide (GL-3) and related glycolipids. α-Galactosidase A gene knockout (Gla KO) mice have no α-galactosidase A activity and progressively accumulate GL-3 in tissues and fluids, similarly to FD patients. The nature and temporal effects of the progressive substrate accumulation on tissue histology in these mice have not previously been characterized. Here, we report the pathology of young to old (3 to 17 months old) Gla KO mice and compare these changes with those in strain-matched control animals. Gla KO mice accumulated GL-3 in various tissues and fluids with age. Lysosomal GL-3 inclusions increased with age in multiple cell types, including renal epithelial, intestinal, and vascular smooth muscle cells, and neurons in trigeminal and dorsal root ganglia, as detected by light and electron microscopy. However, unlike the case for male FD patients with the type 1 classic phenotype, GL-3 inclusions were not detected in vascular endothelial cells or cardiomyocytes. The histological changes in Gla KO mice better resemble the type 2 later-onset phenotype observed in patients with residual α-galactosidase A activity. GL-3 accumulation in the small intestine and sensory ganglia of Gla KO mice provides a model for study of enteropathy and neuropathy in Fabry disease.

X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity and markedly increased erythrocyte protoporphyrin levels. Patients present with severe cutaneous photosensitivity and may develop liver dysfunction. XLP was originally reported as X-linked dominant with 100% penetrance in males and females. We characterized 11 heterozygous females from six unrelated XLP families and show markedly varying phenotypic and biochemical heterogeneity, reflecting the degree of X-chromsomal inactivation of the mutant gene. ALAS2 sequencing identified the specific mutation and confirmed heterozygosity among the females. Clinical history, plasma and erythrocyte protoporphyrin levels were determined. Methylation assays of the androgen receptor and zinc-finger MYM type 3 short tandem repeat polymorphisms estimated each heterozygotes X-chromosomal inactivation pattern. Heterozygotes with equal or increased skewing, favoring expression of the wild-type allele had no clinical symptoms and only slightly increased erythrocyte protoporphyrin concentrations and/or frequency of protoporphyrin-containing peripheral blood fluorocytes. When the wild-type allele was preferentially inactivated, heterozygous females manifested the disease phenotype and had both higher erythrocyte protoporphyrin levels and circulating fluorocytes. These findings confirm that the previous dominant classification of XLP is inappropriate and genetically misleading, as the disorder is more appropriately designated XLP.

Fabry disease is an X-linked lysosomal storage disease due to deficient α-galactosidase A (α-Gal A) activity and the resultant lysosomal accumulation of globotriaosylceramide (Gb3) and related lipids primarily in blood vessels, kidney, heart, and other organs. The renal distribution of stored glycolipid species in the α-Gal A knockout mouse model was compared to that in mice to assess relative distribution and absolute amounts of accumulated sphingolipid isoforms. Twenty isoforms of five sphingolipid groups were visualized by mass spectrometry imaging (MSI), and their distribution was compared with immunohistochemical (IHC) staining of Gb3, the major stored glycosphingolipid in consecutive tissue sections. Quantitative bulk lipid analysis of tissue sections was assessed by electrospray ionization with tandem mass spectrometry (ESI-MS/MS). In contrast to the findings in wild-type mice, all three analytical techniques (MSI, IHC, and ESI-MS/MS) revealed increases in Gb3 isoforms and ceramide dihexosides (composed mostly of galabiosylceramides), respectively. To our knowledge, this is the first report of the distribution of individual molecular species of Gb3 and galabiosylceramides in kidney sections in Fabry disease mouse. In addition, the spatial distribution of ceramides, ceramide monohexosides, and sphingomyelin forms in renal tissue is presented and discussed in the context of their biosynthesis.