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ABSTRACTPatients with pathogenic variants in the TANGO2 gene suffer from severe and recurrent rhabdomyolysis episodes precipitated by fasting. Autophagy functioning was analyzed in vitro, in primary skeletal myoblasts from TANGO2 patients, in basal and fasting conditions, and TANGO2 mutations were associated with reduced LC3-II levels upon starvation. In zebrafish larvae, tango2 inhibition induced locomotor defects which were exacerbated by exposure to atorvastatin, a compound known to cause rhabdomyolysis. Importantly, rhabdomyolysis features of tango2 knockdown were associated with autophagy and mitophagy defects in zebrafish. Calpeptin treatment was sufficient to rescue the locomotor properties thanks to its beneficial effect on autophagy functioning in zebrafish and to improve LC3-II levels in starved primary muscle cells of TANGO2 patients. Overall, we demonstrated that TANGO2 plays an important role in autophagy thus giving rise to new therapeutic perspectives in the prevention of RM life-threatening episodes.

We present the case of a 36-year-old female who was diagnosed at birth with CHI that caused severe hypoglycaemia unresponsive to Diazoxide. Subtotal pancreatectomy was performed at the age of three weeks. Later, histological analysis of her pancreas in a research setting revealed a focal form of CHI. Genetic testing was not available at that time. The patient developed pancreatic exocrine deficiency and insulin-dependent diabetes at the age of 9 years. In 2016, a genetic test revealed a missense heterozygous variant in the ABCC8 gene inherited from her father and classified as having a recessive inheritance. The geneticist concluded that the risk of CHI for her offspring would be low (1/600), making pregnancy favourable. As there was no consanguinity in the family, testing the future father was deemed unnecessary (carrier frequency 1/150 in the general population). The pregnancy occurred spontaneously in 2020 and at a gestational age of 28 weeks, the mother went into premature labour. An emergency C-section was performed in April 2021 resulting in the birth of bichorial bi-amniotic male twins. Following birth, both newborns experienced persistent severe hypoglycaemia which required glucagon treatment and intravenous glucose infusion initially, followed by Diazoxide from day 51 after birth, without satisfactory response. Continuous intravenous Octreotide treatment was introduced on day 72. Due to the recurrence of hypoglycaemia episodes despite reaching maximum doses of Octreotide, from day 92 the treatment was switched to Pasireotide. Genetic tests revealed the same genotypes for both infants: the exon 39 missense variant (c.4716C>A; p.Ser1572Arg) inherited from their mother and a truncating variant in exon 28 (c.3550del; p.Val1184*), inherited from their asymptomatic father. As a result of inheriting two recessive variants of the ABCC8 gene, the children were diagnosed with a diffuse form of CHI, consistent with the diazoxide-unresponsive presentation. This situation is very rare outside consanguinity. This case emphasises the significance of genetic counselling for individuals with a history of rare diseases outside the context of consanguinity, as there is a potential risk of recurrence. Prenatal diagnosis can lead to better outcomes for affected neonates, as well as help families make informed decisions about future pregnancies.

Abstract Background Treatment recommendations for urea cycle disorders (UCDs) include supplementation with amino acids involved in the urea cycle (arginine and/or citrulline, depending on the enzyme deficiency), to maximize ammonia excretion through the urea cycle, but limited data are available regarding the use of citrulline. This study retrospectively reviewed clinical and biological data from patients with UCDs treated with citrulline and/or arginine at a reference center since 1990. The aim was to describe the prescription, impact, and safety of these therapies. Data collection included patient background, treatment details, changes in biochemical parameters (plasma ammonia and amino acids concentrations), decompensations, and patient outcomes. Results Overall, 79 patients (median age at diagnosis, 0.9 months) received citrulline and/or arginine in combination with a restricted protein diet, most with ornithine transcarbamylase (n = 57, 73%) or carbamoyl phosphate synthetase 1 (n = 15, 19%) deficiencies. Most patients also received ammonium scavengers. Median follow-up was 9.5 years and median exposure to first treatment with arginine + citrulline, citrulline monotherapy, or arginine monotherapy was 5.5, 2.5, or 0.3 years, respectively. During follow-up, arginine or citrulline was administered at least once (as monotherapy or in combination) in the same proportion of patients (86.1%); the overall median duration of exposure was 5.9 years for arginine + citrulline, 3.1 years for citrulline monotherapy, and 0.6 years for arginine monotherapy. The most common switch was from monotherapy to combination therapy (41 of 75 switches, 54.7%). During treatment, mean ammonia concentrations were 35.9 µmol/L with citrulline, 49.8 µmol/L with arginine, and 53.0 µmol/L with arginine + citrulline. Mean plasma arginine concentrations increased significantly from the beginning to the end of citrulline treatment periods (from 67.6 µmol/L to 84.9 µmol/L, P

Abstract Congenital hyperinsulinism (HI) is an inappropriate insulin secretion by the pancreatic β-cells secondary to various genetic disorders. The incidence is estimated at 1/50, 000 live births, but it may be as high as 1/2, 500 in countries with substantial consanguinity. Recurrent episodes of hyperinsulinemic hypoglycemia may expose to high risk of brain damage. Hypoglycemias are diagnosed because of seizures, a faint, or any other neurological symptom, in the neonatal period or later, usually within the first two years of life. After the neonatal period, the patient can present the typical clinical features of a hypoglycemia: pallor, sweat and tachycardia. HI is a heterogeneous disorder with two main clinically indistinguishable histopathological lesions: diffuse and focal. Atypical lesions are under characterization. Recessive ABCC8 mutations (encoding SUR1, subunit of a potassium channel) and, more rarely, recessive KCNJ11 (encoding Kir6.2, subunit of the same potassium channel) mutations, are responsible for most severe diazoxide-unresponsive HI. Focal HI, also diazoxide-unresponsive, is due to the combination of a paternally-inherited ABCC8 or KCNJ11 mutation and a paternal isodisomy of the 11p15 region, which is specific to the islets cells within the focal lesion. Genetics and 18F-fluoro-L-DOPA positron emission tomography (PET) help to diagnose diffuse or focal forms of HI. Hypoglycemias must be rapidly and intensively treated to prevent severe and irreversible brain damage. This includes a glucose load and/or a glucagon injection, at the time of hypoglycemia, to correct it. Then a treatment to prevent the recurrence of hypoglycemia must be set, which may include frequent and glucose-enriched feeding, diazoxide and octreotide. When medical and dietary therapies are ineffective, or when a focal HI is suspected, surgical treatment is required. Focal HI may be definitively cured when the partial pancreatectomy removes the whole lesion. By contrast, the long-term outcome of diffuse HI after subtotal pancreatectomy is characterized by a high risk of diabetes, but the time of its onset is hardly predictable.

Low protein diet and sodium or glycerol phenylbutyrate, two pillars of recommended long-term therapy of individuals with urea cycle disorders (UCDs), involve the risk of iatrogenic growth failure. Limited evidence-based studies hamper our knowledge on the long-term effects of the proposed medical management in individuals with UCDs. We studied the impact of medical management on growth and weight development in 307 individuals longitudinally followed by the Urea Cycle Disorders Consortium (UCDC) and the European registry and network for Intoxication type Metabolic Diseases (E-IMD). Intrauterine growth of all investigated UCDs and postnatal linear growth of asymptomatic individuals remained unaffected. Symptomatic individuals were at risk of progressive growth retardation independent from the underlying disease and the degree of natural protein restriction. Growth impairment was determined by disease severity and associated with reduced or borderline plasma branched-chain amino acid (BCAA) concentrations. Liver transplantation appeared to have a beneficial effect on growth. Weight development remained unaffected both in asymptomatic and symptomatic individuals. Progressive growth impairment depends on disease severity and plasma BCAA concentrations, but cannot be predicted by the amount of natural protein intake alone. Future clinical trials are necessary to evaluate whether supplementation with BCAAs might improve growth in UCDs.

Background: Lipin-1 deficiency is a life-threatening disease that causes severe rhabdomyolysis (RM) and chronic symptoms associated with oxidative stress. In the absence of treatment, Hydroxychloroquine sulfate (HCQ) was administered to patients off label use on a compassionate basis in order to improve their physical conditions. Methods: Eleven patients with LPIN1 mutations were treated with HCQ. Clinical and biological efficacy and tolerance were assessed, including pain and quality of life, physical capacities, cardiopulmonary parameters, creatine kinase levels and plasma proinflammatory cytokines. To explore a dose-dependent effect of HCQ, primary myoblasts from 4 patients were incubated with various HCQ concentrations in growth medium (GM) or during starvation (EBSS medium) to investigate autophagy and oxidative stress. Findings: Under HCQ treatment, patient physical capacities improved. Abnormal cardiac function and peripheral muscle adaptation to exercise were normalized. However, two patients who had the highest mean blood HCQ concentrations experienced RM. We hypothesized that HCQ exerts deleterious effects at high concentrations by blocking autophagy, and beneficial effects on oxidative stress at low concentrations. We confirmed in primary myoblasts from 4 patients that high in vitro HCQ concentration (10 µM) but not low concentration (1 µM and 0.1 µM) induced autophagy blockage by modifying endolysosomal pH. Low HCQ concentration (1 µM) prevented reactive oxygen species (ROS) and oxidized DNA accumulation in myoblasts during starvation. Interpretation: HCQ improves the condition of patients with lipin-1 deficiency, but at low concentrations. In vitro, 1 µM HCQ decreases oxidative stress in myoblasts whereas higher concentrations have a deleterious effect by blocking autophagy.

BACKGROUND:To improve our understanding of urea cycle disorders (UCDs) prospectively followed by two North American (NA) and European (EU) patient cohorts. AIMS:Description of the NA and EU patient samples and investigation of the prospects of combined and comparative analyses for individuals with UCDs. METHODS:Retrieval and comparison of the data from 1095 individuals (NA: 620, EU: 475) from two electronic databases. RESULTS:The proportion of females with ornithine transcarbamylase deficiency (fOTC-D), particularly those being asymptomatic (asfOTC-D), was higher in the NA than in the EU sample. Exclusion of asfOTC-D resulted in similar distributions in both samples. The mean age at first symptoms was higher in NA than in EU patients with late onset (LO), but similar for those with early (≤ 28 days) onset (EO) of symptoms. Also, the mean age at diagnosis and diagnostic delay for EO and LO patients were similar in the NA and EU cohorts. In most patients (including fOTC-D), diagnosis was made after the onset of symptoms (59.9%) or by high-risk family screening (24.7%), and less often by newborn screening (8.9%) and prenatal testing (3.7%). Analysis of clinical phenotypes revealed that EO patients presented with more symptoms than LO individuals, but that numbers of symptoms correlated with plasma ammonium concentrations in EO patients only. Liver transplantation was reported for 90 NA and 25 EU patients. CONCLUSIONS:Combined analysis of databases drawn from distinct populations opens the possibility to increase sample sizes for natural history questions, while comparative analysis utilizing differences in approach to treatment can evaluate therapeutic options and enhance long-term outcome studies.

Abstract Background Patients with maple syrup urine disease (MSUD) experiencing metabolic decompensations have traditionally been treated with branched-chain amino acid (BCAA)-free mixture via oral or nasogastric administration routes. In some patients, enteral administration is not possible, either because the patient presents with vomiting, coma, or refuses nasogastric administration, thus intravenous (IV) BCAA-free solution is an appropriate intervention for these challenging cases. Aims This study aimed to evaluate the effectiveness and safety of managing metabolic decompensations by administering an IV BCAA-free solution. Methods This is an observational prospective study of data from MSUD patients hospitalised for decompensation episodes between 2010 and 2016 at 6 centres for rare metabolic diseases in France. Results A total of 24 patients (16 males; 8 females) experiencing 126 MSUD metabolic decompensation episodes (39 in children; 87 in adults) were admitted to hospital. At presentation, mean leucine plasma concentration was ≥ 381 µmol/L in 113/126 (89.7%) episodes. Children were treated with continuous IV BCAA-free solution at doses of 0.8 to 2.0 g/kg/day, for 4.8 days and adults for 3.8 days at doses of 0.5 to 2.6 g/kg/day. In the efficacy set of 102 analysable episodes leucine concentrations were normalised (to below 381 µmol/L) in 82% (n = 18/22) of episodes in children and in 84% (n = 67/80) of episodes in adults. Mean time to leucine normalisation was 3.0 days. This was significantly (p

Hereditary tyrosinemia type 1 (HT1) is a rare autosomal recessive disorder of phenylalanine and tyrosine catabolism due to a deficiency of fumarylacetoacetate hydrolase. HT1 has a large clinical spectrum with acute forms presenting before six months of age, subacute forms with initial symptoms occurring between age 6 and 12 months, and chronic forms after 12 months of age. Without treatment, HT1 results in the accumulation of toxic metabolites leading to liver disease, proximal tubular dysfunction, and porphyria-like neurological crises. Since the early nineties, the outcome of HT1 has dramatically changed due to its treatment with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC, nitisinone). In some countries, HT1 is included in the newborn screening program based on the analysis of succinylacetone concentration on dried blood spots.In the present study, we report clinical and laboratory parameters data on 33 HT1 patients focusing on clinical presentation and therapeutic management at the time of diagnosis. Eighteen patients were diagnosed with the acute form (median age at presentation 2.5 months), 6 with the subacute form (median age at presentation 10 months), and 5 with the chronic form of HT1 (median age at presentation 15 months). Four patients were diagnosed pre-symptomatically in the setting of a family history of HT1. Among the 29 symptomatic patients, hepatomegaly was found in 83% of patients and prolonged coagulation times due to hepatocellular insufficiency was observed in 93% of patients. HT1 diagnosis was confirmed by increased urine succinylacetone in all patients. All patients but 2 were treated with nitisinone immediately at diagnosis. During follow-up, 2 patients received liver transplant for high grade dysplasia or hepatocellular carcinoma, 10 patients exhibited some form of neurocognitive impairments.Our data confirm that HT1 is a severe treatable liver disease that should be detected at the earliest, ideally by newborn screening and appropriately treated.

Abstract Maple syrup urine disease (MSUD) is a rare inborn metabolic disorder, managed with a strict protein‐restricted diet. At any time or age patients may still experience metabolic decompensations, requiring administration of branched chain amino acid (BCAA)‐free formula to reduce leucine levels. This retrospective observational study of 126 decompensation episodes from 54 MSUD patients treated at five centers in France and Germany from 2010 to 2016, describes episodes and outcomes for patients stratified into groups who received enteral/oral or intravenous (IV) BCAA‐free formula, and by pediatric or adult age categories. IV administration of BCAA‐free formula was required in cases of gastric intolerance (33%), refusal to undergo nasogastric tubing (31%), “emergency” (14%) or coma patients (8%), and as prophylaxis before surgery (6%). Overall, mean duration of hospitalization was 6.6 days with oral/enteral BCAA‐free formula and 5.4 days with IV formula. Leucine levels at discharge decreased by a mean of 548.5 μmol/L (69.3%) in the oral/enteral group and 657.2 μmol/L (71.3%) in the IV group. In the pediatric subgroup, there were no marked differences between administration groups on any outcome. In the adult subgroup, mean time to episode resolution was 15.8 days in the oral/enteral group and 7.7 days in the IV group (P = .008); mean duration of hospitalization was 6 days in the oral/enteral group and 4.6 days in the IV group (P = NS). Overall, seven serious adverse events in two patients were reported, of which only nausea and vomiting were treatment related.

Abstract Background Chronic kidney disease (CKD) is one of the main long-term prognosis factors in methylmalonic acidemia (MMA), a rare disease of propionate catabolism. Our objective was to precisely address the clinical and biological characteristics of long-term CKD in MMA adolescent and adult patients. Patients and methods In this retrospective study, we included MMA patients older than 13 years who had not received kidney and/or liver transplantation. We explored tubular functions, with special attention to proximal tubular function. We measured glomerular filtration rate (mGFR) by iohexol clearance and compared it to estimated glomerular filtration rate (eGFR) by Schwartz formula and CKD-EPI. Results Thirteen patients were included (M/F = 5/8). Median age was 24 years (13 to 32). Median mGFR was 57 mL/min/1.73 m2 (23.3 to 105 mL/min/1.73 m2). Ten out of 13 patients had mGFR below 90 mL/min/1.73 m2. No patient had significant glomerular proteinuria. No patient had complete Fanconi syndrome. Only one patient had biological signs suggestive of incomplete proximal tubulopathy. Four out of 13 patients had isolated potassium loss, related to a non-reabsorbable anion effect of urinary methylmalonate. Both Schwartz formula and CKD-EPI significantly overestimated GFR. Bias were respectively 16 ± 15 mL/min/1.73 m2 and 37 ± 22 mL/min/1.73 m2. Conclusion CKD is a common complication of the MMA. Usual equations overestimate GFR. Therefore, mGFR should be performed to inform therapeutic decisions such as dialysis and/or transplantation. Mild evidence of proximal tubular dysfunction was found in only one patient, suggesting that other mechanisms are involved.

Classic galactosemia is a rare inborn error of galactose metabolism with a birth prevalence of about 1/30,000–60,000. Long-term complications occurring despite dietary treatment consist of premature ovarian insufficiency (POI) and neurodevelop mental impairments. We performed with the French Reference Centers for Rare Diseases a multisite collaborative questionnaire survey for classic galactosemic patients. Its primary objective was to assess their puberty, pregnancy, gonadotropic axis, and pelvic morphology by ultrasound. The secondary objective was to determine predictive factors for pregnancy without oocyte donation. Completed questionnaires from 103 patients, 56 female s (median age, 19 years (3–52 years)) and 47 males (median age, 19 years (3–45 years)), were analyzed. Among the 43 females older than 13 years old, mean age for breast develop ment first stage was 13.8 years; spontaneous menarche occurred in 21/31 females at a mean age of 14.6 years. In these 21 women, 62% had spaniomenorrhea and 7/17 older than 30 years had amenorrhea. All age-groups confounded, FSH was above refere nce range for 65.7% of the patients, anti-Müllerian hormone and inhibin B were undetectable, and the ovaries were small with few or no follicles detected. Among the 5 females who sought to conceive, 4 had pregnancies. Among the 47 males, 1 had cryptorchidism, al l have normal testicular function and none had a desire to conceive children. Thus, spontaneous puberty and POI are both common in this population. Spontaneous menarche se ems to be the best predictive factor for successful spontaneous pregnancy.

Transcription of mitochondrial DNA generates long polycistronic precursors whose nucleolytic cleavage yields the individual mtDNA-encoded transcripts. In most cases, this cleavage occurs at the 5′- and 3′-ends of tRNA sequences by the concerted action of RNAseP and RNaseZ/ELAC2 endonucleases, respectively. Variants in the ELAC2 gene have been predominantly linked to severe to mild cardiomyopathy that, in its milder forms, is accompanied by variably severe neurological presentations. Here, we report five patients from three unrelated families. Four of the patients presented mild to moderate cardiomyopathy and one died at 1 year of age, one patient had no evidence of cardiomyopathy. The patients had variable neurological presentations that included intellectual disability, ataxia, refractory epilepsy, neuropathy and deafness. All patients carried previously unreported missense and nonsense variants. Enzymatic analyses showed multiple OXPHOS deficiencies in biopsies from two patients, whereas immunoblot analyses revealed a decreased abundance of ELAC2 in fibroblasts from three patients. Northern blot analysis revealed an accumulation of unprocessed mt-tRNAVal-precursor consistent with the role of ELAC2 in transcript processing. Our study expands the genetic spectrum of ELAC2-linked disease and suggests that cardiomyopathy is not an invariably present clinical hallmark of this pathology.

Water-soluble vitamins play an essential coenzyme role in the nervous system. Acquired vitamin deficiencies are easily treatable, however, without treatment, they can lead to irreversible complications. This study aimed to provide clinical, laboratory parameters and neuroimaging data on vitamin deficiencies in an attempt to facilitate early diagnosis and prompt supplementation. From July 1998 to July 2023, patients at Necker-Enfants-Malades Hospital presenting with acute neurological symptoms attributed to acquired vitamin deficiency were included. Clinical data were extracted from Dr Warehouse database. Neuroimaging, biochemical and electrophysiological data were reviewed. Patients with vitamin B1 deficiency exhibited abnormal eye movements (n = 4/4), fluctuations in consciousness (n = 3/4), and ataxia (n = 3/4). Brain MRI showed alterations of fourth ventricle region (n = 4/4), periaqueductal region (n = 4/4), tectum (n = 3/4), and median thalami (n = 3/4). Patients with vitamin B2 deficiency presented with early onset hypotonia (n = 3/4), hyperlactatemia (n = 4/4), and hyperammonemia (n = 4/4). Plasma acylcarnitines revealed a multiple acyl-coA dehydrogenase deficiency-like profile (n = 4/4). In vitamin B12 deficiency, young children presented with developmental delay (n = 7/7) and older children with proprioceptive ataxia (n = 3/3). Brain MRI revealed atrophy (n = 7/7) and spinal MRI hyperintensity in posterior cervical columns (n = 3/3). Metabolic findings showed elevated methylmalonic acid (n = 6/7) and hyperhomocysteinemia (n = 6/7). Patients with vitamin C deficiency exhibited gait disturbances and muscle weakness (n = 2/2). Acquired vitamin deficiencies may display reversible clinical symptoms mimicking inherited metabolic disorders. Some situations raise suspicion for diagnosis: concordant clinical presentation, suggestive neuroimaging findings, and/or biochemical evidence. Any acute neurological condition should be treated without waiting for definitive biochemical confirmation. • Although they are not extensively documented, vitamin deficiencies do occur in children. • Acquired vitamin deficiencies are easily treatable but without treatment, can lead to irreversible neurological complications. • One should consider a vitamin deficiency in the presence of unexplained neurological symptoms. • One should consider a vitamin deficiency in an exclusively breastfed infant showing signs of developmental stagnation. • Initiation vitamin supplementation should not be delayed pending conclusive biochemical confirmation. [ABSTRACT FROM AUTHOR]

Abstract Background Phosphomannomutase 2 deficiency (PMM2‐CDG) is the most common congenital disorder of glycosylation (CDG). Hypoglycemia has been reported in various CDG including PMM2‐CDG. The frequency and etiology of hypoglycemia in PMM2‐CDG are not well studied. Methods We conducted a systematic review of the literature on genetically and/or biochemically confirmed PMM2‐CDG patients who developed hypoglycemia. Prospective follow‐up information on the patients who received diazoxide therapy was collected and evaluated. Results A total of 165 peer‐reviewed articles reporting on 933 PMM2‐CDG patients were assessed. Hypoglycemia was specifically mentioned only in 23 of these patients (2.5%). Hyperinsulinism was identified in 10 patients (43% of all hypoglycemic patients). Among these 10 patients, seven were successfully treated with diazoxide. However, most patients remained on therapy longer than a year to stay free of hypoglycemia. Conclusion Hypoglycemia is a rarely reported finding in patients with PMM2‐CDG. Diazoxide‐responsive hyperinsulinism was found to have a good prognosis on medication in our PMM2‐CDG patients with hypoglycemia. No genotype‐phenotype correlation was observed with respect to hyperinsulinism. A prospective study should be undertaken to explore the hypothesis that hypoglycemia is underdiagnosed in PMM2‐CDG and to evaluate whether hyperinsulinism is always associated with hypoglycemia.

Pediatric-onset ataxias often present clinically as developmental delay and intellectual disability, with prominent cerebellar atrophy as a key neuroradiographic finding. Here we describe a new clinically distinguishable recessive syndrome in 12 families with cerebellar atrophy together with ataxia, coarsened facial features and intellectual disability, due to truncating mutations in the sorting nexin gene SNX14, encoding a ubiquitously expressed modular PX domain-containing sorting factor. We found SNX14 localized to lysosomes and associated with phosphatidylinositol (3,5)-bisphosphate, a key component of late endosomes/lysosomes. Patient-derived cells showed engorged lysosomes and a slower autophagosome clearance rate upon autophagy induction by starvation. Zebrafish morphants for snx14 showed dramatic loss of cerebellar parenchyma, accumulation of autophagosomes and activation of apoptosis. Our results characterize a unique ataxia syndrome due to biallelic SNX14 mutations leading to lysosome-autophagosome dysfunction.

TMEM165-CDG has first been reported in 2012 and manganese supplementation was shown highly efficient in rescuing glycosylation in isogenic KO cells. The unreported homozygous missense c.928G>C; p.Ala310Pro variant leading to a functional but unstable protein was identified. This patient was diagnosed at 2 months and displays a predominant bone phenotype and combined defects in N-, O- and GAG glycosylation. We administered for the first time a combined D-Gal and Mn2+ therapy to the patient. This fully suppressed the N-; O- and GAG hypoglycosylation. There was also striking improvement in biochemical parameters and in gastrointestinal symptoms. This study offers exciting therapeutic perspectives for TMEM165-CDG. [ABSTRACT FROM AUTHOR]

Abstract Background Trimethylaminuria (TMAU) is a metabolic disorder characterized by the excessive excretion of the malodorous compound trimethylamine (TMA). The diagnosis of TMAU is challenging because this disorder is situated at the boundary between biochemistry and psychiatry. Here, we used nuclear magnetic resonance spectroscopy to assess TMAU in 13 patients. We also sequenced the FMO3 gene in 11 of these patients. Treatment with vitamin B2 was prescribed. Results Two patients (aged 3 and 9 years at the initial consultation) had a particularly unpleasant body odor, as assessed by their parents and the attending physicians. The presence of high urine TMA levels confirmed the presence of a metabolic disorder. The two (unrelated) children carried compound heterozygous variants in the FMO3 gene. In both cases, vitamin B2 administration decreased TMA excretion and reduced body odor. The 11 adults complained of an unpleasant body odor, but the physicians did not confirm this. In all adult patients, the urine TMA level was within the normal range reported for control (non-affected) subjects, although two of the patients displayed an abnormally high proportion of oxidized TMA. Seven of the 9 tested adult patients had a hypomorphic variant of the FMO3 gene; the variant was found in the homozygous state, in the heterozygous state or combined with another hypomorphic variant. All 11 adults presented a particular psychological or psychiatric phenotype, with a subjective perception of unpleasant odor. Conclusions The results present the clinical and biochemical data of patients complaining of unpleasant body odor. Contrary to adult patients, the two children exhibited all criteria of recessively inherited trimethylaminuria, suspected by parents in infancy. B2 vitamin treatment dramatically improved the unpleasant body odor and the ratio of TMA/Cr vs TMAO/Cr in the urine in the children. Other patients presented a particular psychological or psychiatric phenotype.

Context: A strictly controlled diet (often involving enteral tube feeding (ETF)) is part of the treatment of many inherited metabolic diseases (IMDs). Objective: To describe the use of ETF in a large cohort of patients with IMDs. Design: A retrospective analysis of ETF in patients with urea cycle disorders (UCDs), organic aciduria (OA), maple syrup disease (MSUD), glycogen storage diseases (GSDs) or fatty acid oxidation disorders (FAODs) diagnosed before the age of 12 months. Setting: The reference center for IMDs at Necker Hospital (Paris, France). Results: 190 patients born between January 1991 and August 2017 were being treated for OA (n = 60), UCDs (n = 55), MSUD (n = 32), GSDs (n = 26) or FAODs (n = 17). Ninety-eight of these patients (52%) received ETF (OA subgroup: n = 40 (67%); UCDs: n = 12 (22%); MSUD: n = 9 (28%); GSDs: n = 23 (88%); FAODs: n = 14 (82%)). Indications for ETF were feeding difficulties in 64 (65%) patients, cessation of fasting in 39 (40%), and recurrent metabolic decompensation in 14 (14%). Complications of ETF were recorded in 48% of cases, more frequently with nasogastric tube (NGT) than with gastrostomy. Among patients in whom ETF was withdrawn, the mean duration of ETF was 5.9 (SD: 4.8) years (range: 0.6–19.8 years). The duration of ETF was found to vary from one disease subgroup to another (p = 0.051). While the longest median duration was found in the GSD subgroup (6.8 years), the shortest one was found in the UCD subgroup (0.9 years). Conclusion: ETF is an integral part of the dietary management of IMDs. The long duration of ETF and the specific risks of NGT highlights the potential value of gastrostomy.In this study at a French tertiary hospital, we documented the indications, modalities, duration and complications of enteral tube feeding in a cohort of patients with inherited metabolic diseases.

Lipin-1 is a Mg2+-dependent phosphatidic acid phosphatase (PAP) that in mice is necessary for normal glycerolipid biosynthesis, controlling adipocyte metabolism, and adipogenic differentiation. Mice carrying inactivating mutations in the Lpin1 gene display the characteristic features of human familial lipodystrophy. Very little is known about the roles of lipin-1 in human adipocyte physiology. Apparently, fat distribution and weight is normal in humans carrying LPIN1 inactivating mutations, but a detailed analysis of adipose tissue appearance and functions in these patients has not been available so far. In this study, we performed a systematic histopathological, biochemical, and gene expression analysis of adipose tissue biopsies from human patients harboring LPIN1 biallelic inactivating mutations and affected by recurrent episodes of severe rhabdomyolysis. We also explored the adipogenic differentiation potential of human mesenchymal cell populations derived from lipin-1 defective patients. White adipose tissue from human LPIN1 mutant patients displayed a dramatic decrease in lipin-1 protein levels and PAP activity, with a concomitant moderate reduction of adipocyte size. Nevertheless, the adipose tissue develops without obvious histological signs of lipodystrophy and with normal qualitative composition of storage lipids. The increased expression of key adipogenic determinants such as SREBP1, PPARG, and PGC1A shows that specific compensatory phenomena can be activated in vivo in human adipocytes with deficiency of functional lipin-1.