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Alkaptonuria (AKU) is a rare genetic disorder where oxidised homogentisic acid accumulates in connective tissues, leading to multisystem disease. The clinical evaluation Alkaptonuria Severity Score Index (cAKUSSI) is a composite score that assesses the extent of AKU disease. However, some components assess similar disease features, are difficult to measure reliably or cannot be measured in resource-limited environments. cAKUSSI data from the 4-year SONIA 2 randomised controlled trial, which investigated nitisinone treatment in adults with AKU, were analysed (

In an open‐label, controlled study of nitisinone in alkaptonuria (SONIA 2), patients were advised to lower dietary protein intake to reduce serum tyrosine (s‐Tyr) levels and the risk of keratopathy. A body weight increase was observed in the nitisinone‐treated patients but not in the control group. To investigate the effectiveness and consequence of protein restriction in patients with alkaptonuria, a post‐hoc analysis of SONIA 2 was performed. One hundred and thirty‐eight patients were randomised (nitisinone: n = 69, controls: n = 69). Comparison of baseline and Month 12 data on 24‐h urinary excretion of HGA (u‐HGA24) and urea (u‐urea24, used as an approximate protein intake measure), tyrosine and body weight were performed using paired t tests. Comparisons of data between groups were made using 2‐sample t tests. We found that u‐urea24 decreased more in nitisinone‐treated than controls. The study centre with lowest average s‐Tyr and u‐urea24 (nitisinone arm) at Month 12 also had lowest keratopathy incidence (3.1%), while the centre with highest values showed the highest (14.6%). S‐Tyr was generally high in those with keratopathy, but those without keratopathy had similar elevated values. A similar pattern across centres was seen for body weight changes, with a statistically significant weight increase in nitisinone‐treated patients at centres with lower u‐urea24 values. Therefore, in nitisinone‐treated patients, protein restriction led to increased body weight but may also have lowered the risk of developing keratopathies. If introduced, a protein‐restricted diet should be supervised by a dietician and, when appropriate, include amino acid supplements deficient in tyrosine and phenylalanine, to avoid malnutrition and undesired weight increase.

Background Outcomes from studies employing nitisinone 10 mg and 2 mg in alkaptonuria were compared. Patients and methods Sixty‐nine patients in each of the nitisinone (10 mg daily) and controls of suitability of nitisinone in alkaptonuria 2 (SONIA 2), as well as 37 and 23 in nitisinone (2 mg daily) and control cohorts at the National Alkaptonuria Centre (NAC), respectively, were followed up for 4 years. Severity of alkaptonuria (AKU) was assessed by the AKU Severity Score Index (AKUSSI). 24‐h urine homogentisic acid (uHGA24), serum HGA (sHGA), serum tyrosine (sTYR) and serum nitisinone (sNIT) were also analysed at each time point. Dietetic support was used in the NAC, but not in SONIA 2. Safety outcomes were also compared. All statistical analyses were post hoc. Results The slope of the AKUSSI was 0.55, 0.19, 0.30, and 0.06 per month in the control NAC, nitisinone NAC, control SONIA 2, and nitisinone SONIA 2 cohorts, respectively. The intersection of the slopes on the x‐axis was −132, −411, −295, and − 1460 months, respectively. The control and nitisinone slope comparisons were statistically significant both in the NAC (p

Alkaptonuria is a rare inherited disorder for which there was no disease-modifying treatment. In order to develop a successful approved therapy of AKU multiple barriers had to be overcome. These included activities before the conduct of the study including deciding on the drug therapy, the dose of the drug to be used, clarify the nature of the disease, develop outcome measures likely to yield a positive outcome, have a strategy to ensure appropriate patient participation through identification, build a consortium of investigators, obtain regulatory approval for proposed investigation plan and secure funding. Significant barriers were overcome during the conduct of the multicentre study to ensure harmonisation. Mechanisms were put in place to recruit and retain patients in the study. Barriers to patient access following completion of the study and regulatory approval were resolved.

Four patients, from three families, with alkaptonuria receiving 4‐hydroxyphenylpyruvate dioxygenase‐inhibiting nitisinone therapy, which lowers homogentisic acid and increases tyrosine, developed vitiligo. Three of the four patients were receiving nitisinone 2 mg daily, while the fourth was on 10 mg daily. All four patients were either receiving or had received transiently proton‐pump inhibitors as therapy for dyspepsia. The ages of the patients were 35, 42, 40, and 67 years, respectively. Three patients were men and one was a woman. All four patients were either taking a proton‐pump inhibitor or had been taking one at some point. Three of the four were of South Asian and one of Caucasian background. The three patients with South Asian background also had either a personal or family history of autoimmune disease. Distressing vitiligo, initially in an acrofacial distribution, developed unexpectedly in these four patients, before then progressing to involve other parts of the body. Potential factors in the appearance of vitiligo in this setting, including nitisinone and other drug therapy, are explored and responses to the appearance of vitiligo are discussed.

Osteoarthritis (OA) is one of the most prevalent conditions in the world, particularly in the developed world with a significant increase in cases and their predicted impact as we move through the twenty-first century and this will be exacerbated by the covid pandemic. The degeneration of cartilage and bone as part of this condition is becoming better understood but there are still significant challenges in painting a complete picture to recognise all aspects of the condition and what treatment(s) are most appropriate in individual causes. OA encompasses many different types and this causes some of the challenges in fully understanding the condition. There have been examples through history where much has been learnt about common disease(s) from the study of rare or extreme phenotypes, particularly where Mendelian disorders are involved. The often early onset of symptoms combined with the rapid and aggressive pathogenesis of these diseases and their predictable outcomes give an often-under-explored resource. It is these “rarer forms of disease” that William Harvey referred to that offer novel insights into more common conditions through their more extreme presentations. In the case of OA, GWAS analyses demonstrate the multiple genes that are implicated in OA in the general population. In some of these rarer forms, single defective genes are responsible. The extreme phenotypes seen in conditions such as Camptodactyly Arthropathy-Coxa Vara-pericarditis Syndrome, Chondrodysplasias and Alkaptonuria all present potential opportunities for greater understanding of disease pathogenesis, novel therapeutic interventions and diagnostic imaging. This review examines some of the rarer presenting forms of OA and linked conditions, some of the novel discoveries made whilst studying them, and findings on imaging and treatment strategies.

Alkaptonuria is a rare inherited disorder for which there was no disease-modifying treatment. In order to develop a successful approved therapy of AKU multiple barriers had to be overcome. These included activities before the conduct of the study including deciding on the drug therapy, the dose of the drug to be used, clarify the nature of the disease, develop outcome measures likely to yield a positive outcome, have a strategy to ensure appropriate patient participation through identification, build a consortium of investigators, obtain regulatory approval for proposed investigation plan and secure funding. Significant barriers were overcome during the conduct of the multicentre study to ensure harmonisation. Mechanisms were put in place to recruit and retain patients in the study. Barriers to patient access following completion of the study and regulatory approval were resolved.

A large alkaptonuria (AKU) cohort was studied to better characterise the poorly understood phenotype of aortic stenosis of rare disease AKU.Eighty-one patients attended the National Alkaptonuria Centre (NAC) between 2007 and 2020. Nine only attended once. Fifty-one attended more than once and received nitisinone 2 mg daily. Twenty-one attended at least twice without receiving nitisinone. Assessments included questionnaire analysis, standard transthoracic echocardiography, as well as photographs of ochronotic pigment in eyes and ears at baseline when 2 mg nitisinone was commenced, and yearly thereafter. Blood and urine samples were collected for chemical measurement. The prevalence of aortic stenosis and aortic valve replacement were 22.2 and 6.2% in the current group. Aortic maximum velocity (Vmax) was directly related to varying degrees to age (R = 0.58, p 0.001), systolic blood pressure (R = 0.32, p 0.05), serum homogentisic acid (sHGA) (R = 0.28, p 0.05), ochronosis scores (R = 0.72, p 0.001), and alkaptonuria severity score index (AKUSSI) (R = 0.58, p 0.001) on linear regression analysis. Age and ochronosis scores were significantly related to Vmax on multiple regression analysis (p 0.005). Nitisinone decreased sHGA, 24-h urine HGA (uHGAAortic valve disease is highly prevalent in this NAC cohort, and strongly associated with ochronosis and disease severity. Nitisinone decreases ochronosis and had a similar significant effect on Vmax.

Osteoarthritis (OA) is one of the major causes of disability and pain worldwide, yet despite a massive international research effort, no effective disease-modifying drugs have been identified to date. In this review, we put forward the proposition that greater focus on rarer forms of OA could lead to a better understanding of the pathogenesis of more common OA. We have investigated the severe osteoarthropathy of the ultra-rare disease alkaptonuria (AKU). In addition to the progress made in finding a treatment for AKU, our research has revealed important lessons for more common OA, including the identification of high-density mineralized protrusions (HDMPs), new pathoanatomical structures which may play an important role in joint destruction and pain in AKU and in OA. AKU is an inherited disorder of tyrosine metabolism, caused by genetic lack of the enzyme homogentisate 1,2 dioxygenase (HGD), which leads to failure to breakdown homogentisic acid (HGA). While most HGA is excreted over time, some of it is deposited as a pigment in connective tissues, a process described as ochronosis. Ochronotic pigment alters the mechanical properties of tissues, leading to inevitable joint destruction and frequently to cardiac valve disease. Until recently, there was no effective therapy for AKU, but preclinical studies demonstrated that upstream inhibition of tyrosine metabolism by nitisinone, a drug previously used in hereditary tyrosinaemia 1 (HT1), completely prevented ochronosis in AKU mice. This was followed by successful clinical trials which have resulted in nitisinone being approved for therapy of AKU by the European Medicines Agency, making AKU the only cause of OA for which there is an effective therapy to date. Study of other rare causes of OA should be a higher priority for researchers and funders to ensure further advances in understanding and eventual therapy of OA.

Background: Vaccination is an integral aspect of a pediatrician's practice. The fear associated withpain is a common problem. Alleviating this pain, not only puts the child at ease but also reduces theapprehension some parents have. Our objective was to evaluate local analgesic use during childhoodimmunization, its efficacy, and assessing how it serves as an advantage to the patient, theparents/guardian, and the medical personnel. Methodology: It was a randomized study. Data wascollected for a period of 1 year, from August 2018 to August 2019. Children from birth to 18 yearswere divided into 2 groups: case (local anesthetic i.e Lidocaine aerosol applied) and control (no localanesthetics applied). They were immunized as per NIS/IAP. The pain was assessed by a standardpain chart (Modified Behavioural Pain Scale (BPS). Result: Totally (including IM, SC, and IDinjections), the Local anesthesia group Median pain score was 6 and the No Local anesthesia groupMedian pain score was 8. There was a significant difference in pain scores between the two groups.Conclusion: The present study showed that local anesthetics could be applied quickly and withease. There was a significant difference in pain scores between the two groups (higher score beingin the group in which local anesthetics weren’t used). The reduction in the pain score, in turn,showed a significant difference in the attitude of the child, parent, as well as medical personnel.

Osteoporosis and fractures are common features of alkaptonuria. A large cohort of alkaptonuria (AKU) patients was studied to better recognise and characterise osteoporosis and fractures in AKU. Assessments including questionnaire analysis, DEXA and CT densitometry at the neck of femur (FN), total hip (TH) and lumbar spine (LS) were performed on patients at baseline when 2 mg nitisinone was commenced, and yearly thereafter. Blood and urine samples were collected for chemical measurement. CT BMD Z-scores were generated. Between June 2007 and March 2020, 87 AKU patients attended the NAC. At baseline, there were 48 fractures in 39 patients. Prevalence of osteoporosis was 3.1 at FN, 10.8 at TH and 24.7% at LS respectively. Prevalence of fragility fractures was greatly increased at 44.8%. The group with fractures showed increased ochronosis scores (p < 0.05). CT LS showed an inverse relationship with fractures (R = − 0.28; p < 0.05). CT LS was significantly lower in the fracture group (p < 0.002). Following nitisinone only, CT FN and CT TH decreased significantly (p < 0.05 and 0.01 respectively). Following nitisinone plus antiresorptive therapy, CT FN, CT TH and CT LS all increased significantly (p < 0.05, 0.05 and 0.001 respectively). However, patients on nitisinone plus antiresorptive had more fractures than nitisinone and no-treatment groups (p < 0.05). Osteopenia and fragility fractures are common in AKU.. Anti-resorptive therapy increased BMD in AKU without decreasing fragility fractures. Bone densitometry measurements by DXA are less reliable than quantitative CT at the LS in AKU.

Mutations in SQSTM1 are strongly associated with Paget's disease of bone (PDB), but little is known about the clinical characteristics of those with early disease. Radionuclide bone scans, biochemical markers of bone turnover, and clinical characteristics were analyzed in SQSTM1 mutation carriers who took part in the Zoledronic acid in the Prevention of Paget's disease (ZiPP) study. We studied 222 individuals, of whom 54.9% were female, with mean ± SE age of 50.1 ± 0.6 years. Twelve SQSTM1 mutations were observed, including p.Pro392Leu, which was present in 141 of 222 (63.5%) subjects. Bone scan examination revealed evidence of PDB in 20 subjects (9.0%), ten of whom (50%) had a single affected site. Participants with lesions were older than those without lesions but the difference was not significant (53.6 ± 9.1 versus 49.8 ± 8.9; p = .07). The mean age of participants with lesions was not significantly different from the age at which their parents were diagnosed with PDB (55 years versus 59 years, p = .17). All individuals with lesions were asymptomatic. Serum concentrations of total alkaline phosphatase (ALP) normalized to the upper limit of normal in each center were higher in those with lesions (0.75 ± 0.69 versus 0.42 ± 0.29 arbitary units; p

BackgroundAlkaptonuria (AKU) is a disorder of tyrosine/protein metabolism leading to accumulation of homogentisic acid. Clinical management historically recommended reducing dietary protein intake, especially in childhood, which has since been discredited in the literature. For the first time, analysis of baseline cross-sectional nutritional surveillance data from a large cohort of AKU patients is presented, which has clinical implications in all aspects of treatment planning.MethodSeventy-four patients (mean 55 years) admitted to the National Alkaptonuria Centre (NAC), underwent a global nutritional assessment, which included objective anthropometry, bioimpedance measures, habitual nutritional intake using a 7-day food diary and key nutritional biomarkers, including 24 hours urinary nitrogen, serum albumin, total protein and total 25-hydroxy vitamin D. All data was compared with cohort norms or recommended nutrient intakes for health (RNI). The potential beneficial impact of protein and anti-inflammatory nutrients such as vitamin C, selenium, and zinc were statistically interrogated against the AKU severity score index (AKUSSI)-a validated measure of disease progression stratified by age.ResultsFifty percent of AKU patients reported some level of protein restriction at some point in their lives. In comparison with national data sets, AKU patients present with significantly lower than predicted mid-upper arm circumference, grip strength, BMI, total energy and protein intake, and higher than predicted percentage body fat. They therefore meet the ESPEN criteria as "clinically undernourished." Severity fluctuates over the life course. No statistical association is identified between protein intake, expressed as %RNI or g/kg, or anti-inflammatory nutrients, including vitamin C as a high dose supplement on the severity of the disease, when correlated against the validated AKUSSI score.ConclusionAKU patients are at risk of protein depletion associated with a "perfect storm" of risk factors: historical, poorly evidenced recommendations to reduce total protein intake; limited mobility as the condition progresses, compromising muscle integrity; frequent hospital admissions for major surgery associated with multiple joint replacements, creating pinch points of high metabolic demand and the potential impact of the disease itself. As this is the first time this risk has been identified, the authors consider the dietetic implications of nitisinone treatment, which requires dietary protein control to manage the acquired tyrosinaemia. The lack of statistically significant evidence to support dietary manipulation of any kind to impede disease progression in AKU is demonstrated.

For over two decades, nitisinone (NTBC) has been successfully used to manipulate the tyrosine degradation pathway and save the lives of many children with hereditary tyrosinaemia type 1. More recently, NTBC has been used to halt homogentisic acid accumulation in alkaptonuria (AKU) with evidence suggesting its efficacy as a disease modifying agent. NTBC-induced hypertyrosinaemia has been associated with cognitive impairment and potentially sight-threatening keratopathy. In the context of a non-lethal condition (ie, AKU), these serious risks call for an evaluation of the wider impact of NTBC on the tyrosine pathway. We hypothesised that NTBC increases the tyrosine pool size and concentrations in tissues. In AKU mice tyrosine concentrations of tissue homogenates were measured before and after treatment with NTBC. In humans, pulse injection with l-[13 C9 ]tyrosine and l-[d8 ]phenylalanine was used along with compartmental modelling to estimate the size of tyrosine pools before and after treatment with NTBC. We found that NTBC increased tyrosine concentrations in murine tissues by five to nine folds. It also significantly increased the tyrosine pool size in humans (P

Background Alkaptonuria (AKU) is an ultrarare and multifaceted disease characterized by the absence of functional homogentisate 1,2-dioxygenase activity, the enzyme responsible for breakdown of homogentisic acid-a tyrosine-degradation product. The presymptomatic phase of the disease makes diagnosis difficult, with many patients unidentified or diagnosed late in life. Objective To date, no study has analyzed the perceived impact of different symptoms or the experiences of individuals through the patient journey in the context of AKU. This study aimed to examine patients' perceptions of AKU symptoms and their impact on quality of life as well as patients' experiences of being diagnosed and living with the disease. Methods Data for this study were collected using a quantitative self-report questionnaire administered online to people with AKU. Results Data from 45 participants indicate that symptoms with the highest impact for patients are those related to pain and ruptures, disability and inability to perform normal routines, emotional/mental health issues, and heart complications. Findings also revealed significant delays in contact with healthcare services and time to diagnosis. Furthermore, patients reported difficulty in receiving information about AKU, treatment and care, and long-term disease management support. Conclusions Time to diagnosis and care of AKU is significantly delayed. Symptoms of AKU with the highest impact on quality of life for patients are those related to pain and disability and the inability to perform normal routines. Bridging any gaps between patients with AKU and healthcare professionals through education could help improve patients' experiences with AKU through the patient journey.

Homogentisic acid (HGA) lowering, disease modifying off-label nitisinone therapy has been used in the United Kingdom National Alkaptonuria Centre (NAC) since 2012. This study evaluated the serendipitous observation of cataract in a large cohort of patients with the very rare disease alkaptonuria (AKU), over a 5-year period. Patients with AKU who attended the NAC since 2012. Standard physical examination and ocular assessment, including photographs of the crystalline lens were taken before commencement of nitisinone 2 mg daily and annually over 5 years. Photographs were randomised and graded by two independent observers using the WHO cataract classification. AKU patients who did not receive nitisinone were included as a control group. HGA was measured on acidified 24 h urine (u-HGA

New opportunities have arisen for development of therapies for rare diseases with the increased focus and progress in the field. However, standardised framework integrating individual initiatives has not been formed. We present lessons learned and best practice from a collaborative success case in developing a treatment for a rare genetic disease. Our unique consortium model incorporated several of the identified developments under one project, DevelopAKUre, truly bringing together academia, industry and patient organisations in clinical drug development. We found that the equal partnership between all parties in our consortium was a key success factor creating a momentum based on a strong organisational culture where all partners had high engagement and taking ownership of the entire programme. With an agreed mutual objective, this provided synergies through connecting the strengths of the individual parties. Another key success factor was the central role of the patient organisation within the management team, and their unique study participants’ advocacy role securing the understanding and meeting the needs of the clinical study participants in real-time. This resulted in an accelerated enrolment into the clinical studies with a high retention rate allowing for delivery of the programme with significantly improved timelines. Our project was partly funded through an external EU research grant, enabling our model with equal partnership. Further attention within the community should be given to establishing a functional framework where sustainable funding and risk sharing between private and public organisations allow for our model to be replicated.

Little is documented on whether nitisinone-induced hypertyrosinaemia alters cognitive functioning or leads to worsening depression in alkaptonuria (AKU). Wechsler Adult Intelligence Scale-IV (WAIS-IV) and Beck Depression Inventory-II (BDI-II) assessments were performed before and annually following treatment with nitisinone 2 mg daily to assess the impact on cognitive functioning and severity of depression. Serum tyrosine concentrations were also measured annually. WAIS-IV: 63 patients (27 females/36 males: mean age[years] [±standard deviation, range] 55.7[13.7, 26-79]; 60.3[9.6, 19-75]) were included at baseline for assessment of: verbal comprehension (VC), perceptual reasoning (PR), working memory (WM), and processing speed (PS) using separate indices. Over the 6-year period studied 43, 39, 36, 29, 26 and 15 patients had annual assessments. Using a longitudinal model (age and sex adjusted) no significant differences were observed in any of the indices over this period, apart from VC which showed a significant increase after adjustment for sex (p BDI-II: 74 patients (32 females/42 males: mean age[years] [±standard deviation, range] 56.1[13.2, 26-79]; 42 males, 51.5[16.3, 19-70]) were included at baseline. Over the 7-year period studied 48, 47, 38, 34, 32, 24 and 12 patients had annual assessments. No significant differences in BDI-II scores were observed when compared to baseline. Hypertyrosinaemia was observed in all patients following treatment with nitisinone (p

BACKGROUND: Alkaptonuria (AKU) is caused by homogentisate 1,2-dioxygenase deficiency that leads to homogentisic acid (HGA) accumulation, ochronosis and severe osteoarthropathy. Recently, nitisinone treatment, which blocks HGA formation, has been effective in AKU patients. However, a consequence of nitisinone is elevated tyrosine that can cause keratopathy. The effect of tyrosine and phenylalanine dietary restriction was investigated in nitisinone-treated AKU mice, and in an observational study of dietary intervention in AKU patients. METHODS: Nitisinone-treated AKU mice were fed tyrosine/phenylalanine-free and phenylalanine-free diets with phenylalanine supplementation in drinking water. Tyrosine metabolites were measured pre-nitisinone, post-nitisinone, and after dietary restriction. Subsequently an observational study was undertaken in 10 patients attending the National Alkaptonuria Centre (NAC), with tyrosine >700μmol/L who had been advised to restrict dietary protein intake and where necessary, to use tyrosine/phenylalanine-free amino acid supplements. RESULTS: Elevated tyrosine (813μmol/L) was significantly reduced in nitisinone-treated AKU mice fed a tyrosine/phenylalanine-free diet in a dose responsive manner. At 3 days of restriction, tyrosine was 389.3μmol/L, 274.8μmol/L and 144.3μmol/L with decreasing phenylalanine doses. In contrast, tyrosine was not effectively reduced in mice by a phenylalanine-free diet; at 3 days tyrosine was 757.3μmol/L, 530.2μmol/L and 656.2μmol/L, with no dose response to phenylalanine supplementation. In NAC patients, tyrosine was significantly reduced (p=0.002) when restricting dietary protein alone, and when combined with tyrosine/phenylalanine-free amino acid supplementation; 4 out of 10 patients achieved tyrosine

Alkaptonuria is an ultra-rare autosomal recessive disorder of tyrosine metabolism, whereby the homogentisate 1,2-dioxygenase (HGD) enzyme is deficient, causing an elevation of its substrate homogentisic acid (HGA). Overtime, elevated HGA causes connective tissue ochronosis, leading to a severe and early onset osteoarthropathy. The use of HGD deficient mouse models in this metabolic bone disease have provided the opportunity to investigate AKU pathophysiology and potential treatments. An ENU mutagenesis AKU mouse model (BALB/c Hgd−/−) provided the means to explore the onset of pigmentation in cartilage and treatment of AKU with nitisinone, an inhibitor of the upstream enzyme forming HGA. This work provided evidence that nitisinone could not only lower circulating HGA, but could also prevent ochronosis and halt disease progression, leading to its off-label use at the National Alkaptonuria Centre (Liverpool, UK) and its subsequent testing in human clinical trials (DevelopAKUre). Recently, a new targeted AKU mouse model (Hgd tm1a−/−, C57BL/6) has been established, offering a LacZ reporter gene for localising gene expression and LoxP and FRT sites that enabled generation of an inducible and liver-specific HGD knockout model (Hgd tm1d MxCre+/−). This conditional model determined the importance of the liver as a target organ for future gene/enzyme replacement therapies in AKU. The contribution of AKU mouse models has clearly accelerated the treatment and knowledge of this rare disease, and will continue to be used.

The last 15 years have been the most fruitful in the history of research on the metabolic disorder alkaptonuria (AKU). AKU is caused by a deficiency of homogentisate dioxygenase (HGD), the enzyme involved in metabolism of tyrosine, and is characterized by the presence of dark ochronotic pigment in the connective tissue that is formed, due to high levels of circulating homogentisic acid. Almost 120 years ago, Sir Archibald Garrod used AKU to illustrate the concept of Mendelian inheritance in man. In January 2019, the phase III clinical study SONIA 2 was completed, which tested the effectiveness and safety of nitisinone in the treatment of AKU. Results were positive, and they will serve as the basis for the application for registration of nitisinone for treatment of AKU at the European Medicines Agency. Therefore, AKU might become a rare disease for which a cure will be found by 2020. We understand the natural history of the disease and the process of ochronosis much more, but at the same time there are still unanswered questions. One of them is the issue of the factors influencing the varying severity of the disease, since our recent genotype-phenotype study did not show that differences in residual homogentisic acid activity caused by the different mutations was responsible. Although nitisinone has proved to arrest the process of ochronosis, it has some unwanted effects and does not cure the disease completely. As such, enzyme replacement or gene therapy might become a new focus of AKU research, for which a novel suitable mouse model of AKU is available already. We believe that the story of AKU is also a story of effective collaboration between scientists and patients that might serve as an example for other rare diseases.

Objectives We have assessed the effect of elevated concentrations of hydroxyphenylpyruvic acid (HPPA), hydroxyphenyllactic acid (HPLA) and tyrosine, on a range of chemistry tests in serum and urine to explore the potential for chemical interference on routine laboratory analyses in patients with alkaptonuria (AKU) treated with nitisinone and similarly implications for patients with hereditary tyrosinemia type 1 (HT-1). Materials and methods HPPA, HPLA and tyrosine were added separately to pooled serum from subjects without AKU in a range of assays with Roche Modular chemistries. Effects on urine were assessed by changes in urine strip chemistries after mixing a positive control urine with various amounts of the test compounds and reading on a Siemens urine strip meter. Results No significant effect (p > 0.1) was observed up to 225 μmol/L of HPPA and HPLA, and up to 5000 μmol/L tyrosine, on any of the serum-based assays including those with peroxidase-coupled reaction systems of enzymatic creatinine, urate, total cholesterol, HDL cholesterol and triglyceride. Both the monohydroxy HPPA, and the dihydroxy homogentisic acid (HGA), at increased urine concentrations typical of nitisinone-treated AKU and non-treated AKU respectively, did however show marked negative interference in strip assays for glucose and leucocytes; i.e. those with peroxide-linked endpoints. The effect of increased HPLA was less marked. Conclusions In patients with AKU or on nitisinone treatment and HT-1 patients on nitisinone, urine strip chemistry testing should be used sparingly, if at all, to avoid false negative reporting. It is recommended that urine assays should be organised with a suitable specialist laboratory.

BackgroundThe homogentisic acid-lowering therapy nitisinone is being evaluated for the treatment of alkaptonuria (AKU) at the National Centre for AKU. Beyond hypertyrosinemia, the wider metabolic consequences of its use are largely unknown. The aim of this work was to evaluate the impact of nitisinone on the serum metabolome of patients with AKU after 12 and 24 months of treatment.MethodsDeproteinized serum from 25 patients with AKU (mean age[±SD] 51.1 ± 14.9 years, 12 male) was analyzed using the 1290 Infinity II liquid chromatography system coupled to a 6550 quadrupole time-of-flight mass spectrometry (Agilent, UK). Raw data were processed using a batch targeted feature extraction algorithm and an accurate mass retention time database containing 469 intermediary metabolites (MW 72-785). Matched entities (±10 ppm theoretical accurate mass and ±0.3 minutes retention time window) were filtered based on their frequency and variability (ResultsEight metabolites increased in abundance (log2 fold change [FC] 2.1-15.2, P 2 FC 1.5-15.5, P ConclusionsEvaluation of the serum metabolome of patients with AKU showed a significant difference in the abundance of several metabolites following treatment with nitisinone, including a number that have not been previously reported; several of these were not related to the tyrosine metabolic pathway.SynopsisNitisinone therapy has a significant impact on several metabolites beyond the tyrosine metabolic pathway, several of which appear to be related to the redox state of the cell.

BACKGROUND Identification of unknown chemical entities is a major challenge in metabolomics. To address this challenge, we developed a comprehensive targeted profiling strategy, combining 3 complementary liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) techniques and in-house accurate mass retention time (AMRT) databases established from commercial standards. This strategy was used to evaluate the effect of nitisinone on the urinary metabolome of patients and mice with alkaptonuria (AKU). Because hypertyrosinemia is a known consequence of nitisinone therapy, we investigated the wider metabolic consequences beyond hypertyrosinemia. METHODS A total of 619 standards (molecular weight, 45–1354 Da) covering a range of primary metabolic pathways were analyzed using 3 liquid chromatography methods—2 reversed phase and 1 normal phase—coupled to QTOF-MS. Separate AMRT databases were generated for the 3 methods, comprising chemical name, formula, theoretical accurate mass, and measured retention time. Databases were used to identify chemical entities acquired from nontargeted analysis of AKU urine: match window theoretical accurate mass ±10 ppm and retention time ±0.3 min. RESULTS Application of the AMRT databases to data acquired from analysis of urine from 25 patients with AKU (pretreatment and after 3, 12, and 24 months on nitisinone) and 18 HGD−/− mice (pretreatment and after 1 week on nitisinone) revealed 31 previously unreported statistically significant changes in metabolite patterns and abundance, indicating alterations to tyrosine, tryptophan, and purine metabolism after nitisinone administration. CONCLUSIONS The comprehensive targeted profiling strategy described here has the potential of enabling discovery of novel pathways associated with pathogenesis and management of AKU.

Alkaptonuria (AKU) is a rare metabolic disorder caused by a deficient enzyme in the tyrosine degradation pathway, homogentisate 1,2-dioxygenase (HGD). In 172 AKU patients from 39 countries, we identified 28 novel variants of the HGD gene, which include three larger genomic deletions within this gene discovered via self-designed multiplex ligation-dependent probe amplification (MLPA) probes. In addition, using a reporter minigene assay, we provide evidence that three of eight tested variants potentially affecting splicing cause exon skipping or cryptic splice-site activation. Extensive bioinformatics analysis of novel missense variants, and of the entire HGD monomer, confirmed mCSM as an effective computational tool for evaluating possible enzyme inactivation mechanisms. For the first time for AKU, a genotype–phenotype correlation study was performed for the three most frequent HGD variants identified in the Suitability Of Nitisinone in Alkaptonuria 2 (SONIA2) study. We found a small but statistically significant difference in urinary homogentisic acid (HGA) excretion, corrected for dietary protein intake, between variants leading to 1% or >30% residual HGD activity. There was, interestingly, no difference in serum levels or absolute urinary excretion of HGA, or clinical symptoms, indicating that protein intake is more important than differences in HGD variants for the amounts of HGA that accumulate in the body of AKU patients.

ObjectivesOchronotic spondyloarthropathy represents one of the main clinical manifestations of alkaptonuria (AKU); however, prospective data and description of the effect of nitisinone treatment are lacking.MethodsPatients with AKU aged 25 years or older were randomly assigned to receive either oral nitisinone 10 mg/day (N=69) or no treatment (N=69). Spine radiographs were recorded yearly at baseline, 12, 24, 36 and 48 months, and the images were scored for the presence of intervertebral space narrowing, soft tissue calcifications, vacuum phenomena, osteophytes/hyperostosis and spinal fusion in the cervical, thoracic and lumbosacral segment at each of the time points.ResultsAt baseline, narrowing of the intervertebral spaces, the presence of osteophytes/hyperostosis and calcifications were the three most frequent radiographic features in AKU. The rate of progression of the five main features during the 4 years, ranked from the highest to lowest was as follows: intervertebral spaces narrowing, calcifications, vacuum phenomena, osteophytes/hyperostosis and fusions. The rate of progression did not differ between the treated and untreated groups in any of the five radiographic parameters except for a slower rate of progression (sum of all five features) in the treatment group compared with the control group (0.45 (1.11) nitisinone vs 0.74 (1.11) controls, p=0.049) in the thoracic segment.ConclusionThe present study shows a relatively slow but significant worsening of radiographic features in patients with AKU over 4 years. Our results demonstrate a modest beneficial effect of 10 mg/day of nitisinone on the slowly progressing spondylosis in AKU during the relatively limited follow-up time.Trial registration numberNCT01916382.