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Ataxia is a common neurological feature of Niemann–Pick disease type C (NPC). In this disease, unesterified cholesterol accumulates in lysosomes of the central nervous system and hepatic cells. Oxidation by reactive oxygen species produces oxysterols that can be metabolised to specific bile acids. These bile acids have been suggested as useful biomarkers to detect NPC. Concentrations of 3β,5α,6β-trihydroxycholanyl glycine (3β,5α,6β-triOH-Gly) and 3β,7β-dihydroxy-5-cholenyl glycine (3β,7β-diOH-Δ5-Gly) were measured in plasma of 184 adults with idiopathic ataxia. All patients were tested with whole genome sequencing containing hereditary ataxia panels, which include NPC1 and NPC2 mutations and other genetic causes of ataxia. Plasma 3β,5α,6β-triOH-Gly above normal (>90 nM) was found in 8 out of 184 patients. One patient was homozygous for the p.(Val1165Met) mutation in the NPC1 gene. The remaining seven included one patient with Friedreich's ataxia and three patients with autoimmune diseases. Oxidative stress is known to be increased in Friedreich's ataxia and in autoimmune diseases. Therefore, this subset of patients possibly shares a common mechanism that determines the increase of this bile acid. In a large cohort of adults with ataxia, plasma 3β,5α,6β-triOH-Gly was able to detect the one patient in the cohort with NPC1 disease, but also detected oxidation of cholesterol by ROS in other disorders. Plasma 3β,7β-diOH-Δ5-Gly is not a potential biomarker for NPC1. [ABSTRACT FROM AUTHOR]

ALDH7A1 deficiency is an epileptic encephalopathy whose seizures respond to treatment with supraphysiological doses of pyridoxine. It arises as a result of damaging variants in ALDH7A1, a gene in the lysine catabolism pathway. α-Aminoadipic semialdehyde (α-AASA) and Δ 1 -piperideine-6-carboxylate (P6C), which accumulate because of the block in the lysine pathway, are diagnostic biomarkers for this disorder. Recently, it has been reported that 6-oxo-pipecolic acid (6-oxo-PIP) also accumulates in the urine, CSF and plasma of ALDH7A1-deficient individuals and that, given its improved stability, it may be a more suitable biomarker for this disorder. This study measured 6-oxo-PIP in urine from a cohort of 30 patients where α-AASA was elevated and showed that it was above the normal range in all those above 6 months of age. However, 6-oxo-PIP levels were within the normal range in 33% of the patients below 6 months of age. Levels increased with age and correlated with a decrease in α-AASA levels. Longitudinal analysis of urine samples from ALDH7A1-deficient patients who were on a lysine restricted diet whilst receiving supraphysiological doses of pyridoxine showed that levels of 6-oxo-PIP remained elevated whilst α-AASA decreased. Similar to α-AASA, we found that elevated urinary excretion of 6-oxo-PIP can also occur in individuals with molybdenum cofactor deficiency. This study demonstrates that urinary 6-oxo-PIP may not be a suitable biomarker for ALDH7A1 deficiency in neonates. However, further studies are needed to understand the biochemistry leading to its accumulation and its potential long-term side effects., (© 2024 The Author(s). Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Alpha-methylacyl-CoA-racemase (AMACR) deficiency (MIM#604489) is a peroxisomal disorder resulting in the accumulation of pristanic acid, dihydroxycholestanoic acid (DHCA), and trihydroxycholestanoic acid (THCA), with variable clinical features and age of onset from infancy to late adulthood. The purpose of this report is to define clinical variations and follow-up data in AMACR deficiency emphasizing treatment with a review of cases reported in the literature. Here, four patients, from two families, diagnosed with AMACR deficiency and showing phenotypic heterogeneity are presented. A 10-month-old-female presented with coagulopathy, hepatic dysfunction, and elevated pristanic acid, DHCA, and THCA levels. Genetic testing confirmed a homozygous variant c.596G>A in the AMACR gene. Her brother who had macrovesicular hepatosteatosis and elevated pristanic acid levels was diagnosed with family screening. The third patient presented with rhabdomyolysis following a strenuous exercise without any other complaint. Homozygous novel c.1006G>A variant was found on the AMACR gene. His asymptomatic sister carrying the same variant also had elevated pristanic acid levels. They had normal neuropsychologic evaluation. Dietary treatment with low phytanic and pristanic acid content was recommended to the patients but all showed poor compliance. The sibling pairs were followed for periods of 11 and 7 years, respectively. AMACR deficiency is usually described as an adult-onset disorder with neuropsychological problems. The characterization of natural history and new clinical phenotypes may support earlier diagnosis and treatment., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

Regulation of H 2 S homeostasis in humans is poorly understood. Therefore, we assessed the importance of individual enzymes in synthesis and catabolism of H 2 S by studying patients with respective genetic defects. We analyzed sulfur compounds (including bioavailable sulfide) in 37 untreated or insufficiently treated patients with seven ultrarare enzyme deficiencies and compared them to 63 controls. Surprisingly, we observed that patients with severe deficiency in cystathionine β-synthase (CBS) or cystathionine γ-lyase (CSE) - the enzymes primarily responsible for H 2 S synthesis - exhibited increased and normal levels of bioavailable sulfide, respectively. However, an approximately 21-fold increase of urinary homolanthionine in CBS deficiency strongly suggests that lacking CBS activity is compensated for by an increase in CSE-dependent H 2 S synthesis from accumulating homocysteine, which suggests a control of H 2 S homeostasis in vivo. In deficiency of sulfide:quinone oxidoreductase - the first enzyme in mitochondrial H 2 S oxidation - we found normal H 2 S concentrations in a symptomatic patient and his asymptomatic sibling, and elevated levels in an asymptomatic sibling, challenging the requirement for this enzyme in catabolizing H 2 S under physiological conditions. Patients with ethylmalonic encephalopathy and sulfite oxidase/molybdenum cofactor deficiencies exhibited massive accumulation of thiosulfate and sulfite with formation of large amounts of S-sulfocysteine and S-sulfohomocysteine, increased renal losses of sulfur compounds and concomitant strong reduction in plasma total cysteine. Our results demonstrate the value of a comprehensive assessment of sulfur compounds in severe disorders of homocysteine/cysteine metabolism and provide evidence for redundancy and compensatory mechanisms in the maintenance of H 2 S homeostasis., Competing Interests: Declaration of competing interest GS declares that he serves as CEO of Colbourne Pharmaceuticals consulting Origin Biosciences in the developments of treatments for MoCD type A, BS is investigator in clinical trials to develop a treatment for MoCD-A sponsored by Origin Biosciences Inc. The other authors do not declare any competing interests., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)