Long-term follow-up of a patient with neonatal form of Gaucher disease.

Gaucher disease is the most common of the lysosomal storage diseases. It presents a wide phenotypic continuum, in which one may identify the classically described phenotypes, including type 1 form with visceral involvement, type 2 acute neuropathic early-infantile form, and type 3 subacute neuronopathic form. At the most severe end there is the perinatal form with onset in utero or during the neonatal period. The very few reported cases of neonatal onset Gaucher disease presented high and early mortality, due to neurological or visceral involvement, including liver failure. We report our experience treating a patient with the neonatal form of Gaucher disease who presented at birth with thrombocytopenia, hepatosplenomegaly and cholestasis. Despite early enzyme replacement therapy, liver disease was progressive. Liver biopsy showed hepatocellular giant-cell transformation, a nonspecific finding consistent with inflammation. The lack of response to enzyme replacement therapy and the microscopic findings suggested that mechanisms apart from substrate accumulation and Gaucher cells may play a role in the hepatic pathogenesis in Gaucher disease. An attempt to use corticosteroids at the age of 3 months resulted in a dramatic improvement in liver function and resulted in long-term survival. The patient is alive and 2 years old at this writing. Our case suggests that inflammatory processes may be important in the early pathogenesis of Gaucher disease and that early use of corticosteroids may open the way to a new therapeutic approach.

Newborn screening of mucopolysaccharidosis type I.

Mucopolysaccharidosis type I (MPS I), a lysosomal storage disease caused by a deficiency of α-L-iduronidase, leads to storage of the glycosaminoglycans, dermatan sulfate and heparan sulfate. Available therapies include enzyme replacement and hematopoietic stem cell transplantation. In the last two decades, newborn screening (NBS) has focused on early identification of the disorder, allowing early intervention and avoiding irreversible manifestations. Techniques developed and optimized for MPS I NBS include tandem mass-spectrometry, digital microfluidics, and glycosaminoglycan quantification. Several pilot studies have been conducted and screening programs have been implemented worldwide. NBS for MPS I has been established in Taiwan, the United States, Brazil, Mexico, and several European countries. All these programs measure α-L-iduronidase enzyme activity in dried blood spots, although there are differences in the analytical strategies employed. Screening algorithms based on published studies are discussed. However, some limitations remain: one is the high rate of false-positive results due to frequent pseudodeficiency alleles, which has been partially solved using post-analytical tools and second-tier tests; another involves the management of infants with late-onset forms or variants of uncertain significance. Nonetheless, the risk-benefit ratio is favorable. Furthermore, long-term follow-up of patients detected by neonatal screening will improve our knowledge of the natural history of the disease and inform better management.

Nutrition in adult patients with selected lysosomal storage diseases.

Lysosomal storage disorders (LSDs) are a group of clinically heterogeneous disorders affecting the function of lysosomes and are characterized by an accumulation of undigested substrates within several cell types. In recent years there have been substantial advances in supportive care and drug treatment for some LSDs, leading to improved patient survival, as seen in Gaucher, Pompe and Fabry disease and some Mucopolysaccharidoses; however, many symptoms still persist. Thus it is now even more important to improve patients' quality of life and reduce symptoms and comorbidities. One potential way of achieving this goal is through adjunct nutritional therapy, which is challenging as patients may be overweight with associated consequences, or malnourished, or underweight. Furthermore, drugs used to treat LSDs can modify the metabolic status and needs of patients. There are currently not enough data to make specific dietary recommendations for individual LSDs; however, suggestions can be made for managing clinical manifestations of the diseases, as well as treatment-associated adverse events. The metabolic and nutritional status of adult patients must be regularly assessed and individualized dietary plans may be created to cater to a patient's specific needs. Damage to the autophagic process is a common feature in LSDs that is potentially sensitive to dietary manipulation and needs to be assessed in clinical studies.

Oxygen and nitrite reduction by heme-deficient sulphite oxidase in a patient with mild sulphite oxidase deficiency.

Isolated sulphite oxidase deficiency (iSOD) is an autosomal recessive inborn error in metabolism characterised by accumulation of sulphite, which leads to death in early infancy. Sulphite oxidase (SO) is encoded by the SUOX gene and forms a heme- and molybdenum-cofactor-dependent enzyme localised in the intermembrane space of mitochondria. Within SO, both cofactors are embedded in two separated domains, which are linked via a flexible 11 residue tether. The two-electron oxidation of sulphite to sulphate occurs at the molybdenum active site. From there, electrons are transferred via two intramolecular electron transfer steps (IETs) via the heme cofactor and to the physiologic electron acceptor cytochrome c. Previously, we reported nitrite and oxygen to serve as alternative electron acceptors at the Moco active site, thereby overcoming IET within SO. Here, we present evidence for these reactions to occur in an iSOD patient with an unusual mild disease representation. In the patient, a homozygous c.427C>A mutation within the SUOX gene leads to replacement of the highly conserved His143 to Asn. The affected His143 is one of two heme-iron-coordinating residues within SO. We demonstrate, that the H143N SO variant fails to bind heme in vivo leading to the elimination of SO-dependent cytochrome c reduction in mitochondria. We show, that sulphite oxidation at the Moco domain is unaffected in His143Asn SO variant and demonstrate that nitrite and oxygen are able to serve as electron acceptors for sulphite-derived electrons in cellulo. As result, the patient H143N SO variant retains residual sulphite oxidising activity thus ameliorating iSOD progression.

The combined use of enzyme activity and metabolite assays as a strategy for newborn screening of mucopolysaccharidosis type I.

Objectives Mucopolysaccharidosis type I (MPS I) was added to our expanded screening panel in 2015. Since then, 127,869 newborns were screened by measuring α-L-iduronidase (IDUA) enzyme activity with liquid chromatography tandem mass spectrometry (LC-MS/MS). High false positives due to frequent pseudodeficiency alleles prompted us to develop a second-tier test to quantify glycosaminoglycan (GAG) levels in dried blood spot (DBS). Methods Heparan-sulfate (HS) and dermatan-sulfate (DS) were measured with LC-MS/MS after methanolysis. DBSs were incubated with methanolic-HCl 3 N at 65 °C for 45 min. Chromatographic separation used an amide column with a gradient of acetonitrile and water with 10 mM ammonium acetate in a 9-min run. The method was validated for specificity, linearity, lower limit of quantification (LOQ), accuracy and precision. Results Intra- and inter-day coefficients of variation were <15% for both metabolites. Reference values in 40 healthy newborns were: HS mean 1.0 mg/L, 0-3.2; DS mean 1.5 mg/L, 0.5-2.7). The two confirmed newborn MPS I patients had elevated HS (4.9-10.4 mg/L, n.v. <3.2) and DS (7.4-8.8 mg/L, n.v. <2.7). Since its introduction in February 2019, the second-tier test reduced the recall rate from 0.046% to 0.006%. Among 127,869 specimens screened, the incidence was 1:63,935 live births. Both patients started enzyme replacement therapy (ERT) within 15 days of birth and one of them received allogenic hematopoietic stem cell transplantation (HSCT) at ht age of 6 months. Conclusions GAGs in DBS increased the specificity of newborn screening for MPS I by reducing false-positives due to heterozygosity or pseudodeficiency. Early diagnosis and therapeutical approach has improved the outcome of our patients with MPS I.

Transatlantic combined and comparative data analysis of 1095 patients with urea cycle disorders-A successful strategy for clinical research of rare diseases.

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.

Plasma and dried blood spot lysosphingolipids for the diagnosis of different sphingolipidoses: a comparative study.

Background Lysosphingolipids, the N-deacylated forms of sphingolipids, have been identified as potential biomarkers of several sphingolipidoses, such as Gaucher, Fabry, Krabbe and Niemann-Pick diseases and in GM1 and GM2 gangliosidoses. To date, different methods have been developed to measure various lysosphingolipids (LysoSLs) in plasma. Here, we present a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for a simultaneous quantification of LysoSLs (HexSph, LysoGb3, LysoGM1, LysoGM2, LysoSM and LysoSM509) in dried blood spot (DBS). This LC-MS/MS method was used to compare the levels of LysoSLs in DBS and plasma in both affected patients and healthy controls. Methods Lysosphingolipids were extracted from a 3.2 mm diameter DBS with a mixture of methanol:acetonitrile:water (80:15:5, v/v) containing internal stable isotope standards. Chromatographic separation was performed using a C18 column with a gradient of water and acetonitrile both with 0.1% formic acid in a total run time of 4 min. The compounds were detected in the positive ion mode electrospray ionization (ESI)-MS/MS by multiple reaction monitoring (MRM). Results The method was validated on DBS to demonstrate specificity, linearity, lowest limit of quantification, accuracy and precision. The reference ranges were determined in pediatric and adult populations. The elevated levels of LysoSLs were identified in Gaucher disease (HexSph), Fabry disease (LysoGb3), prosaposin deficiency (HexSph and LysoGb3) and Niemann-Pick disease types A/B and C (LysoSM and LysoSM509). The correlation in the levels between DBS and plasma was excellent for LysoGb3 and HexSph but poor for LysoSM and LysoSM509. Conclusions Despite the fact that plasma LysoSLs determination remains the gold standard, our LC-MS/MS method allows a rapid and reliable quantification of lysosphingolipids in DBS. The method is a useful tool for the diagnosis of different sphingolipidoses except for Niemann-Pick type C.

Newborn screening for lysosomal storage disorders by tandem mass spectrometry in North East Italy.

BACKGROUND: Lysosomal storage diseases (LSDs) are inborn errors of metabolism resulting from 50 different inherited disorders. The increasing availability of treatments and the importance of early intervention have stimulated newborn screening (NBS) to diagnose LSDs and permit early intervention to prevent irreversible impairment or severe disability. We present our experience screening newborns in North East Italy to identify neonates with Mucopolysaccharidosis type I (MPS I) and Pompe, Fabry, and Gaucher diseases. METHODS: Activities of acid ß-glucocerebrosidase (ABG; Gaucher), acid α-glucosidase (GAA; Pompe), acid α-galactosidase (GLA; Fabry), and acid α-L-iduronidase (IDUA; MPS-I) in dried blood spots (DBS) from all newborns during a 17-month period were determined by multiplexed tandem mass spectrometry (MS/MS) using the NeoLSD® assay system. Enzymatic activity cutoff values were determined from 3500 anonymous newborn DBS. In the screening study, samples were retested if the value was below cutoff and a second spot was requested, with referral for confirmatory testing and medical evaluation if a low value was obtained. RESULTS: From September 2015 to January 2017, 44,411 newborns were screened for the four LSDs. We recalled 40 neonates (0.09%) for collection of a second DBS. Low activity was confirmed in 20, who had confirmatory testing. Ten of 20 had pathogenic mutations: two Pompe, two Gaucher, five Fabry, and one MPS-I. The incidences of Pompe and Gaucher diseases were similar (1/22,205), with Fabry disease the most frequent (1/8882) and MPS-I the rarest (1/44411). The combined incidence of the four disorders was 1/4411 births. CONCLUSIONS: Simultaneously determining multiple enzyme activities by MS/MS, with a focus on specific biochemical markers, successfully detected newborns with LSDs. The high incidence of these disorders supports this screening program.

Correction to: Age at disease onset and peak ammonium level rather than interventional variables predict the neurological outcome in urea cycle disorders.

Due to an unfortunate error during the typesetting process, the collaborators were presented incorrectly.

Correction to: Impact of age at onset and newborn screening on outcome in organic acidurias.

Due to an unfortunate error during the typesetting process, the collaborators were presented incorrectly.

International clinical guideline for the management of classical galactosemia: diagnosis, treatment, and follow-up.

Classical galactosemia (CG) is an inborn error of galactose metabolism. Evidence-based guidelines for the treatment and follow-up of CG are currently lacking, and treatment and follow-up have been demonstrated to vary worldwide. To provide patients around the world the same state-of-the-art in care, members of The Galactosemia Network (GalNet) developed an evidence-based and internationally applicable guideline for the diagnosis, treatment, and follow-up of CG. The guideline was developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. A systematic review of the literature was performed, after key questions were formulated during an initial GalNet meeting. The first author and one of the working group experts conducted data-extraction. All experts were involved in data-extraction. Quality of the body of evidence was evaluated and recommendations were formulated. Whenever possible recommendations were evidence-based, if not they were based on expert opinion. Consensus was reached by multiple conference calls, consensus rounds via e-mail and a final consensus meeting. Recommendations addressing diagnosis, dietary treatment, biochemical monitoring, and follow-up of clinical complications were formulated. For all recommendations but one, full consensus was reached. A 93 % consensus was reached on the recommendation addressing age at start of bone density screening. During the development of this guideline, gaps of knowledge were identified in most fields of interest, foremost in the fields of treatment and follow-up.

Diagnosis of sphingolipidoses: a new simultaneous measurement of lysosphingolipids by LC-MS/MS.

BACKGROUND: Lysosphingolipids (LysoSLs) are derivatives of sphingolipids which have lost the amide-linked acyl chain. More recently, LysoSLs have been identified as storage compounds in several sphingolipidoses, including Gaucher, Fabry and Niemann-Pick diseases. To date, different methods have been developed to measure each individual lysosphingolipid in plasma. This report describes a rapid liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) assay for simultaneous quantification of several LysoSLs in plasma. METHODS: We analyzed the following compounds: hexosylsphingosine (HexSph), globotriaosylsphingosine (LysoGb3), lysosphingomyelin (LysoSM) and lysosphingomyelin-509 (LysoSM-509). The sample preparation requires only 100 µL of plasma and consists of an extraction with a mixture of MeOH/acetone/H2O (45:45:10, v/v). RESULTS: The method validation showed high sensitivity, an excellent accuracy and precision. Reference ranges were determined in healthy adult and pediatric population. The results demonstrate that the LC-MS/MS method can quantify different LysoSLs and can be used to identify patients with Fabry (LysoGb3), Gaucher and Krabbe (HexSph) diseases, prosaposine deficiency (LysoGb3 and HexSph), and Niemann-Pick disease types A/B and C (LysoSM and LysoSM-509). CONCLUSIONS: This LC-MS/MS method allows a rapid and simultaneous quantification of LysoSLs and is useful as a biochemical diagnostic tool for sphingolipidoses.

Age at disease onset and peak ammonium level rather than interventional variables predict the neurological outcome in urea cycle disorders.

BACKGROUND: Patients with urea cycle disorders (UCDs) have an increased risk of neurological disease manifestation. AIMS: Determining the effect of diagnostic and therapeutic interventions on the neurological outcome. METHODS: Evaluation of baseline, regular follow-up and emergency visits of 456 UCD patients prospectively followed between 2011 and 2015 by the E-IMD patient registry. RESULTS: About two-thirds of UCD patients remained asymptomatic until age 12 days [i.e. the median age at diagnosis of patients identified by newborn screening (NBS)] suggesting a potential benefit of NBS. In fact, NBS lowered the age at diagnosis in patients with late onset of symptoms (>28 days), and a trend towards improved long-term neurological outcome was found for patients with argininosuccinate synthetase and lyase deficiency as well as argininemia identified by NBS. Three to 17 different drug combinations were used for maintenance therapy, but superiority of any single drug or specific drug combination above other combinations was not demonstrated. Importantly, non-interventional variables of disease severity, such as age at disease onset and peak ammonium level of the initial hyperammonemic crisis (cut-off level: 500 µmol/L) best predicted the neurological outcome. CONCLUSIONS: Promising results of NBS for late onset UCD patients are reported and should be re-evaluated in a larger and more advanced age group. However, non-interventional variables affect the neurological outcome of UCD patients. Available evidence-based guideline recommendations are currently heterogeneously implemented into practice, leading to a high variability of drug combinations that hamper our understanding of optimised long-term and emergency treatment.

Impact of age at onset and newborn screening on outcome in organic acidurias.

BACKGROUND AND AIM: To describe current diagnostic and therapeutic strategies in organic acidurias (OADs) and to evaluate their impact on the disease course allowing harmonisation. METHODS: Datasets of 567 OAD patients from the E-IMD registry were analysed. The sample includes patients with methylmalonic (MMA, n = 164), propionic (PA, n = 144) and isovaleric aciduria (IVA, n = 83), and glutaric aciduria type 1 (GA1, n = 176). Statistical analysis included description and recursive partitioning of diagnostic and therapeutic strategies, and odds ratios (OR) for health outcome parameters. For some analyses, symptomatic patients were divided into those presenting with first symptoms during (i.e. early onset, EO) or after the newborn period (i.e. late onset, LO). RESULTS: Patients identified by newborn screening (NBS) had a significantly lower median age of diagnosis (8 days) compared to the LO group (363 days, p < 0.001], but not compared to the EO group. Of all OAD patients 71 % remained asymptomatic until day 8. Patients with cobalamin-nonresponsive MMA (MMA-Cbl(-)) and GA1 identified by NBS were less likely to have movement disorders than those diagnosed by selective screening (MMA-Cbl(-): 10 % versus 39 %, p = 0.002; GA1: 26 % versus 73 %, p < 0.001). For other OADs, the clinical benefit of NBS was less clear. Reported age-adjusted intake of natural protein and calories was significantly higher in LO patients than in EO patients reflecting different disease severities. Variable drug combinations, ranging from 12 in MMA-Cbl(-) to two in isovaleric aciduria, were used for maintenance treatment. The effects of specific metabolic treatment strategies on the health outcomes remain unclear because of the strong influences of age at onset (EO versus LO), diagnostic mode (NBS versus selective screening), and the various treatment combinations used. CONCLUSIONS: NBS is an effective intervention to reduce time until diagnosis especially for LO patients and to prevent irreversible cerebral damage in GA1 and MMA-Cbl(-). Huge diversity of therapeutic interventions hampers our understanding of optimal treatment.

The long-term treatment of a patient with type 1 diabetes mellitus and glutaric aciduria type 1: the effect of insulin.

UNLABELLED: The coexistence of two diseases associated with different metabolic disorders is a very rare event. Some associations, although sporadic, can be particularly challenging both in terms of diagnostic and therapeutic management and in terms of theoretical perspective. Here, we report a child affected by type 1 diabetes mellitus (T1DM) and glutaric aciduria type 1 (GA1). The child was diagnosed with classical T1DM at 15 months of age, with a tendency toward hypoglycemia. A few months later, during an acute intercurrent infective episode, the child displayed acute hypotonia of the lower limbs and limbs dystonia. A brain MRI showed bilateral striatal necrosis, suggesting GA1 diagnosis. Treatment with a low-lysine dietary regimen and carnitine supplementation was started and resulted in an improvement in metabolic control and a reduction of hypoglycemic episodes along with an increasing in insulin daily dose. After 2 years, the neurological outcome consisted of a reduction in dystonic movements and a metabolic stability of both diseases. CONCLUSION: This case provides some insight into the reciprocal interconnections between the two metabolic disorders. Similar pathogenic mechanisms responsible for the neuronal injury might have impacted each other, and a strict relationship between a specific aspect of GA1-impaired metabolism and glucose homeostasis might explain how the tailored management of GA1 was not only effective in controlling the disease, but it also resulted in an improvement in the control of the glycemic profile. What in known: • Glutaric aciduria type 1 (GA1) usually presents in childhood with severe and possibly irreversible neuronal damage, triggered by a catabolic stress • The association of GA1 with other diseases, including type 1 diabetes mellitus (T1DM), is a rare event, complicating the treatment management What is new: • Insulin treatment has a role in preventing GA1 metabolic decompensation, even in the catabolic condition of hypoglycemia • Promoting GA1 metabolic equilibrium by tailoring drug and dietary treatment in our patient affect by T1DM has a positive impact also in improving glycemic balance.

Mutations of the mitochondrial-tRNA modifier MTO1 cause hypertrophic cardiomyopathy and lactic acidosis.

Dysfunction of mitochondrial respiration is an increasingly recognized cause of isolated hypertrophic cardiomyopathy. To gain insight into the genetic origin of this condition, we used next-generation exome sequencing to identify mutations in MTO1, which encodes mitochondrial translation optimization 1. Two affected siblings carried a maternal c.1858dup (p.Arg620Lysfs(∗)8) frameshift and a paternal c.1282G>A (p.Ala428Thr) missense mutation. A third unrelated individual was homozygous for the latter change. In both humans and yeast, MTO1 increases the accuracy and efficiency of mtDNA translation by catalyzing the 5-carboxymethylaminomethylation of the wobble uridine base in three mitochondrial tRNAs (mt-tRNAs). Accordingly, mutant muscle and fibroblasts showed variably combined reduction in mtDNA-dependent respiratory chain activities. Reduced respiration in mutant cells was corrected by expressing a wild-type MTO1 cDNA. Conversely, defective respiration of a yeast mto1Δ strain failed to be corrected by an Mto1(Pro622∗) variant, equivalent to human MTO1(Arg620Lysfs∗8), whereas incomplete correction was achieved by an Mto1(Ala431Thr) variant, corresponding to human MTO1(Ala428Thr). The respiratory yeast phenotype was dramatically worsened in stress conditions and in the presence of a paromomycin-resistant (P(R)) mitochondrial rRNA mutation. Lastly, in vivo mtDNA translation was impaired in the mutant yeast strains.

Characterization of human disease phenotypes associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, and IFIH1.

Aicardi-Goutières syndrome is an inflammatory disease occurring due to mutations in any of TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR or IFIH1. We report on 374 patients from 299 families with mutations in these seven genes. Most patients conformed to one of two fairly stereotyped clinical profiles; either exhibiting an in utero disease-onset (74 patients; 22.8% of all patients where data were available), or a post-natal presentation, usually within the first year of life (223 patients; 68.6%), characterized by a sub-acute encephalopathy and a loss of previously acquired skills. Other clinically distinct phenotypes were also observed; particularly, bilateral striatal necrosis (13 patients; 3.6%) and non-syndromic spastic paraparesis (12 patients; 3.4%). We recorded 69 deaths (19.3% of patients with follow-up data). Of 285 patients for whom data were available, 210 (73.7%) were profoundly disabled, with no useful motor, speech and intellectual function. Chilblains, glaucoma, hypothyroidism, cardiomyopathy, intracerebral vasculitis, peripheral neuropathy, bowel inflammation and systemic lupus erythematosus were seen frequently enough to be confirmed as real associations with the Aicardi-Goutieres syndrome phenotype. We observed a robust relationship between mutations in all seven genes with increased type I interferon activity in cerebrospinal fluid and serum, and the increased expression of interferon-stimulated gene transcripts in peripheral blood. We recorded a positive correlation between the level of cerebrospinal fluid interferon activity assayed within one year of disease presentation and the degree of subsequent disability. Interferon-stimulated gene transcripts remained high in most patients, indicating an ongoing disease process. On the basis of substantial morbidity and mortality, our data highlight the urgent need to define coherent treatment strategies for the phenotypes associated with mutations in the Aicardi-Goutières syndrome-related genes. Our findings also make it clear that a window of therapeutic opportunity exists relevant to the majority of affected patients and indicate that the assessment of type I interferon activity might serve as a useful biomarker in future clinical trials.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation.

BACKGROUND: The clinical presentation of patients with organic acidurias (OAD) and urea cycle disorders (UCD) is variable; symptoms are often non-specific. AIMS/METHODS: To improve the knowledge about OAD and UCD the E-IMD consortium established a web-based patient registry. RESULTS: We registered 795 patients with OAD (n = 452) and UCD (n = 343), with ornithine transcarbamylase (OTC) deficiency (n = 196), glutaric aciduria type 1 (GA1; n = 150) and methylmalonic aciduria (MMA; n = 149) being the most frequent diseases. Overall, 548 patients (69 %) were symptomatic. The majority of them (n = 463) presented with acute metabolic crisis during (n = 220) or after the newborn period (n = 243) frequently demonstrating impaired consciousness, vomiting and/or muscular hypotonia. Neonatal onset of symptoms was most frequent in argininosuccinic synthetase and lyase deficiency and carbamylphosphate 1 synthetase deficiency, unexpectedly low in male OTC deficiency, and least frequently in GA1 and female OTC deficiency. For patients with MMA, propionic aciduria (PA) and OTC deficiency (male and female), hyperammonemia was more severe in metabolic crises during than after the newborn period, whereas metabolic acidosis tended to be more severe in MMA and PA patients with late onset of symptoms. Symptomatic patients without metabolic crises (n = 94) often presented with a movement disorder, mental retardation, epilepsy and psychiatric disorders (the latter in UCD only). CONCLUSIONS: The initial presentation varies widely in OAD and UCD patients. This is a challenge for rapid diagnosis and early start of treatment. Patients with a sepsis-like neonatal crisis and those with late-onset of symptoms are both at risk of delayed or missed diagnosis.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 2: the evolving clinical phenotype.

BACKGROUND: The disease course and long-term outcome of patients with organic acidurias (OAD) and urea cycle disorders (UCD) are incompletely understood. AIMS: To evaluate the complex clinical phenotype of OAD and UCD patients at different ages. RESULTS: Acquired microcephaly and movement disorders were common in OAD and UCD highlighting that the brain is the major organ involved in these diseases. Cardiomyopathy [methylmalonic (MMA) and propionic aciduria (PA)], prolonged QTc interval (PA), optic nerve atrophy [MMA, isovaleric aciduria (IVA)], pancytopenia (PA), and macrocephaly [glutaric aciduria type 1 (GA1)] were exclusively found in OAD patients, whereas hepatic involvement was more frequent in UCD patients, in particular in argininosuccinate lyase (ASL) deficiency. Chronic renal failure was often found in MMA, with highest frequency in mut(0) patients. Unexpectedly, chronic renal failure was also observed in adolescent and adult patients with GA1 and ASL deficiency. It had a similar frequency in patients with or without a movement disorder suggesting different pathophysiology. Thirteen patients (classic OAD: 3, UCD: 10) died during the study interval, ten of them during the initial metabolic crisis in the newborn period. Male patients with late-onset ornithine transcarbamylase deficiency were presumably overrepresented in the study population. CONCLUSIONS: Neurologic impairment is common in OAD and UCD, whereas the involvement of other organs (heart, liver, kidneys, eyes) follows a disease-specific pattern. The identification of unexpected chronic renal failure in GA1 and ASL deficiency emphasizes the importance of a systematic follow-up in patients with rare diseases.