Caregiver-reported outcome measures (CROMs) complement clinical assessments of neurodevelopmental functions (NDF) in pediatric rare disease trials. This scoping review summarizes use of CROMs of NDF across bodily function, activity, and participation domains of the International Classification of Functioning, Disability, and Health (ICF) model in pediatric lysosomal storage disorders (LSDs), characterizes assessed neurodevelopmental domains, and outlines considerations for CROM selection within a comprehensive functional assessment strategy. We applied JBI methodology and adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Primary articles reporting CROM of NDF use in children with LSDs ≤ 12 years old were identified. Study characteristics, design, and CROMs utilized were extracted. CROMs were classified as condition-general or disease-specific. CROM content was mapped to neurodevelopmental domains (activities of daily living [ADL], cognition, communication, physical, social-emotional function). Ninety-eight articles published in the last 10 years reported on 38 distinct CROMs of NDF across > 20 LSDs. Nearly all studies (93%) used ≥ 1 condition-general CROM of NDF, most commonly the Vineland Adaptive Behavioral Scales or the Pediatric Quality of Life Inventory. Eleven disease-specific CROMs were reported, typically alongside condition-general measures. Physical, ADL, and social-emotional domains were indexed most consistently. CROMs were endpoints in 32 LSD clinical trials. Findings illustrate the variety and common trends of CROMs of NDF used in pediatric LSD studies. This review informs selection of complementary caregiver-reported endpoints in LSD trials based on a well-defined, clinically meaningful construct; alignment with other endpoints and expert consensus; and operational practicality.
Gaucher disease is a rare, autosomal recessive disease, with decreased activity of lysosomal glucocerebrosidase (GCase) due to changes in the GBA1 gene. There is no cure for Gaucher disease, and standard treatment involves the use of enzyme replacement therapy or substrate reduction therapy. We describe the first case of Gaucher disease that was treated with an autologous transplant of lentivirus-transduced CD34+ cells. Enzyme therapy was stopped 4 weeks prior to Day 0 of transplant. At 5 years of follow-up, dried blood spot GCase enzyme levels have remained in the normal range; there has been a consistent and sustained reduction of lyso-GB1 and liver volume, and hematological indices such as leukocyte count, hemoglobin, and platelet count have remained in the normal range despite no additional therapy for the Gaucher disease. This case shows a sustained response to a single dose of lentiviral gene therapy for Gaucher disease.
Primary mitochondrial diseases frequently affect the central nervous system, yet the extent, distribution and progression of white matter hyperintensities (WMHs) remain insufficiently characterised, particularly in terms of quantitative volumetrics and longitudinal progression. Although WMHs are typically attributed to cerebral small-vessel disease, mitochondrial disorders may cause white matter injury through distinct vascular and metabolic mechanisms. We conducted a retrospective single-centre study at Turku University Hospital including 36 patients with mitochondrial disease, each with at least one brain MRI (73 images). Longitudinal data were available for 15 patients. Three-dimensional T1-weighted and FLAIR images (1.5/3 T) were analysed with the FDA-cleared cNeuro tool to obtain intracranial volume-normalised WMH and lesion volumes and an automated global Fazekas score. At baseline (median age 49 years), WMHs were present in all supratentorial regions. Over time, WMH volumes increased significantly in periventricular, deep and juxtacortical regions, while lesion progression was predominantly periventricular. Fazekas scores remained generally low and stable. In follow-up imaging, women and patients carrying the m.3243A>G variant showed a greater burden of WMHs and lesions, compared with men and those with other mitochondrial diagnoses. WMH load did not differ according to history of stroke-like episodes. Mitochondrial disease is associated with early and progressive WMH accumulation, particularly in individuals with the m.3243A>G variant, and the pattern exceeds what would be expected from conventional vascular risk factors alone. These findings support a disease-specific mechanism of white matter vulnerability and highlight the importance of quantitative MRI for monitoring progression in mitochondrial disease.
Biallelic pathogenic variants in PNPT1 cause combined oxidative phosphorylation deficiency 13 (COXPD13) (MIM #614932), linking mitochondrial dysfunction to type I interferon (IFN) activation through cytosolic leakage of mitochondrial double-stranded RNA (mt-dsRNA). This mechanism connects mitochondrial disease to interferonopathies such as Aicardi-Goutières syndrome (AGS). We describe a 7-month-old female infant with compound heterozygous PNPT1 variants presenting with severe hypotonia, feeding difficulties necessitating gastrostomy, dystonia, and elevated serum lactate. Brain magnetic resonance imaging (MRI) demonstrated marked cerebellar, brainstem, and basal ganglia atrophy, with a lactate peak on MR spectroscopy (consistent with an inverted doublet). Serum immune profiling revealed a mild but elevated type I IFN signature. Given the mechanistic overlap with AGS, off-label tofacitinib, a Janus kinase (JAK) inhibitor that blocks IFN-driven JAK/STAT signaling, was initiated following pediatric interferonopathy dosing protocols. Tofacitinib was associated with normalization of serum type I IFN biomarkers, reduction in lactate and transaminases, improvement in dystonic movements, ventilatory stability, and improved growth/nutrition without treatment-limiting adverse events. To our knowledge, this represents the first reported use of JAK inhibition in COXPD13. The observed clinical and biochemical stabilization supports defining COXPD13 as a "mitochondrial interferonopathy" and suggests that IFN-signature screening may identify mitochondrial disease patients who could benefit from targeted immunomodulation.
Leukodystrophy due to biallelic HMBS variants is a rare condition distinct from acute intermittent porphyria (AIP). It is characterised by progressive leukoencephalopathy rather than acute attacks of neurovisceral symptoms. We report the ongoing clinical progression of a patient with leukodystrophy due to homozygous variants in HMBS [c.251C>A, p.Ala84Asp] despite liver transplantation. We demonstrate that porphyrin precursor levels are unchanged following liver transplantation in the periphery and that porphyrin precursor levels are constitutively elevated in the cerebrospinal fluid and are not reduced by haem arginate therapy. Liver transplantation and hepatically directed therapies are not likely to be effective for leukodystrophy due to biallelic HMBS variants. Alternative treatment strategies should be developed for effective management of this disorder. One-liner: Leukodystrophy due to biallelic HMBS variants is unlikely to be cured by liver transplantation or other hepatically directed therapies.
Hyperammonemia is a medical emergency, and the cause must be identified quickly in order to treat appropriately. Malnutrition is a known risk factor for hyperammonemia; however, there are limited reliable lab indicators used to identify malnutrition. Early identification of the etiology of hyperammonemia is crucial to optimizing care, specifically reintroduction of appropriate amounts of protein into the diet. Herein, we discuss three patients with complex medical histories and clinical signs of malnutrition who presented with hyperammonemia. In all three patients, both hypoaminoacidemia and pyroglutamic aciduria were observed. Specifically, all patients had low tyrosine, tryptophan, methionine, and branched-chain amino acids. Recognizing this biochemical pattern could result in more rapid initiation of supplementing protein, a primary tenet of treatment in malnutrition-related hyperammonemia. We highlight the unique features of malnutrition-related hyperammonemia, propose mechanisms to explain the pattern, and suggest a framework for managing these cases.
Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal recessive neurometabolic disorder caused by biallelic pathogenic variants in ALDH5A1, encoding the mitochondrial enzyme SSADH. This enzyme catalyses the conversion of succinic semialdehyde to succinic acid in the γ-aminobutyric acid (GABA) degradation pathway. SSADH deficiency leads to the accumulation of neurotoxic metabolites, including γ-hydroxybutyrate (GHB), and presents with developmental delay, hypotonia, ataxia, seizures, behavioral disturbances, and intellectual disability. We report a 10-month-old Caucasian male with global developmental delay, central hypotonia, and delayed motor milestones. He presented acutely with left-sided hemiplegia following irritability and vomiting. Brain MRI showed bilateral (right > left) T2 hyperintensities and diffusion restriction in the globus pallidus. Urine organic acid analysis via gas chromatography-mass spectrometry revealed markedly elevated 4-hydroxybutyric acid and 4,5-dihydroxyhexanoic lactone, pathognomonic for SSADH deficiency. Molecular testing identified compound heterozygous ALDH5A1 variants: c.278G>T p.(Cys93Phe) and c.612G>A p.(Trp204*), both previously reported as pathogenic. Parental segregation confirmed trans configuration. Three weeks postillness, he developed focal seizures, which have remained well controlled on levetiracetam. His seizure onset in infancy is notably earlier than the typical early childhood onset (~9 years) reported in SSADH deficiency. This case expands the phenotypic spectrum of SSADH deficiency to include metabolic stroke as a presenting feature in infancy and highlights the importance of early recognition and molecular confirmation to guide management and emerging therapeutic strategies.
Molybdenum cofactor deficiency (MoCD) is an inborn error of metabolism included in the differential for refractory neonatal seizures. The prognosis is guarded, with a median reported age of death between 2.4 and 3.0 years. Mortality is primarily due to seizures and lower respiratory tract infections. MoCD has a distinct biochemical profile, characterized by elevated urinary S-sulfocysteine, xanthine, and hypoxanthine, and low or undetectable serum and urine uric acid levels. A disease-altering treatment is available for MoCD Type A; however, due to the rarity of the condition, its natural history remains poorly understood. We present a patient with neonatal-onset refractory seizures, whose biochemical testing, performed within 24 h of specimen receipt in the laboratory, revealed a pattern consistent with MoCD. Before the genetics team could disclose the preliminary diagnosis, the patient demised, without evidence of worsening seizures or respiratory infection. Results of genome sequencing, guided by biochemical findings, identified double homozygous pathogenic variants in MOCS1 (associated with MoCD Type A). Although the biochemical genetics laboratory's protocol for analyzing and reporting S-sulfocysteine levels within 48 h enabled a rapid preliminary diagnosis, the patient's condition deteriorated too quickly to initiate disease-altering treatment, progressing more rapidly than described in the literature. We discuss potential hypotheses for his rapid decline and the broader implications for the field of biochemical genetics.
MRPS34 encodes a mitoribosomal protein essential for mitochondrial translation. Biallelic pathogenic variants in MRPS34 cause Combined Oxidative Phosphorylation Deficiency 32 (COXPD32), a rare mitochondrial disorder within the Leigh syndrome spectrum (LSS), ranging from fatal in infancy to adult survival. The objective is to describe two new individuals with MRPS34-related disease and expand the clinical, genetic, and phenotypic spectrum of COXPD32. Clinical, radiological, biochemical, and molecular evaluations were conducted in two individuals with Leigh Syndrome (LS). Exome and genome sequencing identified presumed biallelic MRPS34 variants. A systematic review of all previously reported cases was performed to assess possible genotype-phenotype correlations (n = 11). Individual 1, who died in infancy with LS, was presumed compound heterozygous for a novel splice-site variant (c.364 + 2 T>C, p.(?)) and a nonsense variant (c.94C>T, p.(Gln32*)). Individual 2 survived into mid childhood and was homozygous for the hypomorphic variant c.322-10G>A, p.(?). Among 11 individuals, key features included developmental delay (100%), lactic acidosis (91%), brainstem lesions (91%), and metabolic acidosis (83%). Homozygosity for c.322-10G>A, p.(?) correlated with longer survival. MRPS34-related disease presents with multisystemic features and genotype-dependent severity. Accurate genetic diagnosis is essential for prognosis and therapeutic strategies.
Hereditary tyrosinemia type I (HT-1) is a rare metabolic disorder treated by NTBC, requiring careful therapeutic and nutritional monitoring. While follow-up traditionally relies on urinary succinylacetone, plasma NTBC and plasma amino acids, dried blood spot (DBS) methods have introduced alternative monitoring options. However, the optimal biochemical monitoring remains debated. This study evaluated the clinical utility of NTBC measurements compared with established biomarkers in HT-1. In this retrospective single-centre study, we analysed biological data from 12 HT-1 patients treated with NTBC over 6 years. We analysed correlations between NTBC, succinylacetone, δ-aminolevulinic acid (δ-ALA) and alpha-fetoprotein concentrations, and compared tyrosine and phenylalanine levels in DBS and plasma. Succinylacetone suppression in both urine and blood was achieved across a broad range of NTBC concentrations, suggesting that blood succinylacetone is a more reliable marker of metabolic control than NTBC levels. Elevated urinary δ-ALA levels were observed in some samples despite unquantifiable succinylacetone, indicating that succinylacetone may not fully reflect neurological risk. NTBC concentrations showed limited correlation with alpha-fetoprotein, reinforcing the continued need for imaging in hepatocellular carcinoma surveillance. DBS measurement of tyrosine and phenylalanine displayed variable biases relative to plasma, particularly for tyrosine, highlighting the challenges of using DBS for nutritional monitoring. While NTBC remains central in the treatment of HT-1 patients, its blood concentrations offer limited added value for long-term monitoring. Focusing on succinylacetone measurement, along with δ-ALA and alpha-fetoprotein to evaluate neurological and hepatic risks, is recommended. Plasma remains the preferred matrix for amino acids monitoring. Larger multi-centre studies are needed to confirm these findings.
MRPS22-related mitochondrial disease (MIM#611719) is a rare autosomal recessive disorder caused by defects in the mitochondrial ribosomal protein S22, a component of the small mitoribosomal subunit essential for mitochondrial translation. Of the few reported cases, most present antenatally with a severe phenotype, conveying a poor prognosis. We describe a fetus with severe antenatal-onset MRPS22-related mitochondrial disease and the use of multi-omics in the molecular diagnosis. A primigravida underwent termination of pregnancy following identification of multiple congenital anomalies (hydrops fetalis, microcephaly, corpus callosal agenesis, periventricular cysts and cardiac hypertrophy) on ultrasound at 20 + 2 weeks' gestation, confirmed on fetal magnetic resonance imaging. Trio genome sequencing revealed compound heterozygous variants in MRPS22 (NM_020191.4: c.509G>A; p.(Arg170His) and c.565C>G; p.(Arg189Gly)). Rapid proteomic analysis demonstrated destabilisation of the small mitoribosomal subunit and combined reduction of OXPHOS complexes, supporting the pathogenicity of the variants. This case consolidates the antenatal phenotype of severe MRPS22-related disease and highlights the importance of considering mitochondrial disease in the differential diagnosis of congenital anomalies, especially hydrops fetalis and corpus callosum anomalies. This study provides evidence for the utility of multi-omic approaches (trio genome sequencing, proteomics) in confirming variant pathogenicity following pregnancy loss, enabling accurate diagnosis, and informing reproductive counselling for affected families.
GM1 gangliosidosis is a lysosomal storage disease (LSD) caused by β-galactosidase deficiency, characterized by the accumulation of gangliosides in various tissues. Among different GM1 forms (infantile form, late-infantile and juvenile form, and late-onset form), the infantile form is the most severe: despite an early clinical onset with rapid neurodegeneration, coarse face, abdominal visceromegaly and skeletal abnormalities, the diagnosis is usually delayed, given the lack of recognized early disease-specific markers. We report the case of a newborn presenting with mild edema of hands and feet, mild transient hypoalbuminemia and isolated hyperphosphatasemia at three weeks of life. The first cardiological evaluation showed mild mitral regurgitation. Despite the absence of neurological symptoms, organomegaly, or a coarse face, the turgid consistency of the limbs, together with mitral regurgitation and persistent hyperphosphatasemia, led to multiorgan investigations with discovery of bilateral cherry-red spots and a beak-shaped lumbar vertebra. The cardiological follow-up revealed a dysplastic mitral valve. In the suspicion of a lysosomal disease, biochemical investigations were planned. An altered profile of urinary oligosaccharides, along with low β-galactosidase activity in leukocytes, led to the diagnosis of infantile GM1 gangliosidosis at 3 months of age. The GLB1 gene analysis confirmed the diagnosis. Genetic testing for GLB1 should be considered in cases of persistent hyperphosphatemia, especially if it is associated with any other clinical indicator of GM1, such as limb edema.
Tyrosinemia type 1 (HT1), due to deficient activity of fumarylacetoacetate hydrolase, causes accumulation of succinylacetone (SA). SA concentrations in urine and plasma of untreated HT1 patients are typically several thousand-fold higher than normal, hence are readily recognized by traditional diagnostic methods in most cases. However, quantitation of SA in the nanomolar range is important for monitoring patients treated with nitisinone, for identifying attenuated or atypical forms of HT1, and for confirmation or refutation of the diagnosis of HT1 following a positive newborn screen. Our laboratory, a reference centre for diagnosis and monitoring of HT1, previously assayed SA by gas chromatography-mass spectrometry (GC-MS). Three years ago, we upgraded this method by transferring it to a new triple quadrupole technology (GC-MS/MS). A stable isotope dilution process is used, with sample treatment consisting of an oximation step followed by a single liquid-liquid extraction then trimethylsilyl derivatization. Quantitation is based on intensities of the ion transitions m/z 620 → 181 for SA and 625 → 186 for the internal standard. Method validation demonstrated enhanced analytical specificity and sensitivity, with good precision and accuracy. Using GC-MS/MS instead of GC-MS allowed a limit of quantitation of 1 nmol/L while decreasing the required specimen volumes, as well as reducing the number of sample processing steps, chromatographic run time, and instrument maintenance. This assay facilitates laboratory diagnosis and monitoring of HT1, permits identification and characterization of other hypersuccinylacetonemias including maleylacetoacetate isomerase deficiency, and is also a valuable tool for research studies using animal models and cellular models of HT1.
COASY protein associated neurodegeneration is a rare, progressive autosomal recessive neuroferritinopathy due to pathogenic mutations in the COASY gene, coding for the mitochondrial located coenzyme A synthase. Clinical manifestations include seizures, progressive spasticity, dystonia, neuropathy, cognitive decline and neuropsychiatric abnormalities. Both foetal and childhood onset phenotypes are described. We report three patients with COASY protein associated neurodegeneration who were identified on newborn screening with a dried bloodspot acylcarnitine pattern consistent with carnitine palmitoyltransferase 1a deficiency, that is, an elevated ratio of free carnitine (C0) to the sum of palmitoylcarnitine (C16) and octanoylcarnitine (C18):[C0/(C16+C18)]. Two siblings, who died in infancy, displayed neurological features from birth, with magnetic resonance imaging of the brain displaying immature cortical sulcation, parenchymal atrophy and pontocerebellar hypoplasia. The third patient presented with global developmental delay, pyramidal signs and seizures with brain magnetic resonance imaging at age 15 months demonstrating a thin corpus callosum, symmetric diffusion restriction throughout the basal ganglia and evidence of deposition in the globus pallidus. This report demonstrates that phenotypes of COASY protein associated neurodegeneration should be included in the differential diagnosis of dried blood spot acylcarnitine pattern suggestive of carnitine palmitoyltransferase 1a deficiency and may represent new potential for early diagnosis.
Hypophosphatasia (HPP) is an inherited metabolic disease caused by deficient tissue-nonspecific alkaline phosphatase (ALP) activity and characterized by skeletal and nonskeletal symptoms, including muscle weakness and fatigue. We hypothesized that mitochondrial respiration is impaired in muscle in HPP, independent of skeletal manifestations, and that the second-generation ALP enzyme replacement therapy (ERT) efzimfotase alfa improves respiration. Akp2GW-/- mice were used for this purpose. Body weight, bone mineralization, and survival were validated in Akp2GW-/- mice versus Akp2-/- mice, an established model of HPP. No significant differences were found, validating the Akp2GW-/- model. Respiratory outcomes were measured in skeletal muscle fiber bundles in age- and sex-matched Akp2GW-/- and Akp2GW+/+ (wild-type) mice; bone mineralization was assessed. Mean maximal respiration and mitochondrial spare respiratory capacity (SRC) in vehicle-treated Akp2GW-/- mice were 37% and 30% of values from wild-type mice, respectively, independent of skeletal manifestations. Efzimfotase alfa treatment significantly improved maximal respiration in tissue from Akp2GW-/- mice by 147% versus vehicle (p = 0.0059) and improved SRC by 262% versus vehicle (p = 0.0008). Mean maximal respiration and SRC in tissue from efzimfotase alfa-treated Akp2GW-/- mice were 92% and 107%, respectively, of tissue from wild-type mice. Cellular ultrastructure of muscle biopsies from people with HPP showed atypical mitochondrial morphology, including branching cristae and dispersed matrix. In a mouse model of HPP, we show that the altered mitochondrial respiration in skeletal muscle is improved by ERT and that HPP is characterized by altered muscle mitochondrial morphology in humans. Together, these data suggest ERT could improve muscular symptoms in HPP.
Isovaleric acidemia (IVA) is a rare autosomal recessive disorder caused by isovaleryl-CoA dehydrogenase deficiency, leading to toxic metabolite accumulation and potentially life-threatening metabolic crises. Newborn screening (NBS) has enabled early detection through elevated C5 acylcarnitine levels, yet the prognostic value of initial C5 concentrations remains unclear. This single-center retrospective study examined 10 Australian patients diagnosed with IVA via NBS between 2004 and 2025. Patients were stratified as "mild" or "classic" based on initial C5 levels and clinical severity. Developmental outcomes were assessed using standardized tools and clinical evaluations. Despite biochemical evidence of metabolic instability, including hyperammonemia, acidosis, and hospitalizations, no patients demonstrated neurological impairment on follow-up. Notably, individuals with markedly elevated C5 levels (up to 63.6 μmol/L) remained neurologically intact, suggesting that early diagnosis and timely metabolic management (protein restriction, carnitine/glycine supplementation, emergency protocols) may mitigate long-term CNS involvement. Dietary practices varied, with some patients maintaining protein restriction due to self-limited intake. Our findings reveal substantial heterogeneity in biochemical profiles and clinical trajectories, with minimal correlation between initial C5 levels and neurodevelopmental outcomes. These results align with prior studies questioning the predictive value of isolated NBS markers and support a more nuanced, individualized approach to IVA management. Limitations include small sample size, retrospective design, and incomplete standardized neurocognitive testing. Further prospective studies incorporating genotype data and formal assessments are needed to refine risk stratification and optimize long-term care strategies.
Riboflavin (RF, vitamin B2) is an essential vitamin of which the co-factors are critical to numerous cellular processes. RF is used as a treatment for inherited metabolic diseases (IMDs), although its effectiveness in many disorders has not been established. We aim to summarize all available data on the efficacy and safety of RF in the management of IMDs. A systematic literature search was conducted for articles reporting the effectiveness of RF in IMDs. RF therapy was considered "effective" in an IMD if more than 75% of patients showed a positive response, "uncertain" in case of a positive response in fewer than 75% of patients, and "not effective" if patients deteriorated or died following RF therapy. RF therapy was reported in 381 articles addressing 33 separate IMDs. A positive effect was established in MADD type 3 (n=536, 93.1% responsive), RTD 2,3 (n = 94, 90.4% responsive), ACAD 9 (n = 29, 75.9% responsive), and FAD transporter deficiency (n = 5, 100% responsive). The effect was uncertain in complex I and II deficiency, ethylmalonic encephalopathy, FAD synthase deficiency, glutaric aciduria type 1, L2 hydroxyglutaric aciduria, and MADD type 2. RF was not effective in MADD type 1. Adverse effects were infrequent and mild. RF therapy in MADD type 3, RTD 2 and 3, ACAD9, and FAD transporter deficiency is safe and effective. Access to RF for these patients is crucial. For a substantial group of IMDs, the effect of RF remains uncertain. In these conditions, a trial of RF therapy with clearly defined outcome criteria might be considered.
Carbonic anhydrase VA (CAVA) deficiency (OMIM 114761) is an ultra-rare inborn error of metabolism with fewer than 20 cases described. Affected infants present in the first days of life with hyperammonaemia, lactic acidosis, ketonaemia and encephalopathy. Prenatal genetic testing can facilitate the diagnosis of subsequent affected pregnancies and permit proactive clinical management to prevent metabolic decompensation. Here we describe the clinical course of two sibling infants antenatally diagnosed with CAVA deficiency who were monitored and managed in the newborn period without decompensation. The proband, their older brother, had presented on day four of life with marked lactic acidosis, hyperammonaemia and encephalopathy requiring haemofiltration due to CAVA deficiency. His brothers were each born in a tertiary neonatal setting. They were managed with regular 3-4 hourly breastfeeds with supplementary expressed breast milk and formula top-ups to ensure optimal nutrition. In addition, they received carglumic acid (100 mg/kg daily) for 5 days. Regular biochemical monitoring was undertaken with measurement of acid-base status and ammonia levels. In contrast to their older brother, these male siblings had unremarkable neonatal periods with no significant clinical or biochemical concerns, demonstrating that in a neonate known to be affected with CAVA deficiency, early intervention can be instituted to minimise the risk of metabolic decompensation in the neonatal period.
GABA-transaminase (GABA-T) deficiency is a rare disorder of GABA metabolism characterized by neonatal encephalopathy, epilepsy, hypotonia and intellectual disability. It is caused by biallelic pathogenic variants in the ABAT gene. We report a case of a newborn female born to a G10P5 mother, with abnormal fetal movements and polyhydramnios in utero. At birth, she presented with hypotonia, hypersomnolence, decreased level of consciousness, central hypoventilation, non-epileptic myoclonus, seizures, and neurogenic diabetes insipidus. Brain MRI on day two of life showed partial cerebellar vermis agenesis and cerebellar hemispheric dysplasia. Her EEG demonstrated burst suppression. Family history was significant for two siblings with a similar neonatal course. On rapid whole exome sequencing she was found to be homozygous for a nonsense variant in the ABAT gene designated c.1278C>A, p.Tyr426*. Both of her affected siblings were also found to be homozygous for the same variant, and carrier status was confirmed in both parents. A trial of flumazenil infusion showed subtle EEG improvement. Our report of three siblings with severe GABA-T deficiency provides evidence for founder effect in the Canadian Indigenous population and discusses the utility of urine GABA quantification as a reasonable screening test.
Propionic acidemia is an inborn error of metabolism involving an enzymatic defect of propionyl-CoA carboxylase that results in the build-up of toxic metabolites which can induce metabolic decompensation. Secondary mitochondrial dysfunction in propionic acidemia has been commonly recognized; however, its clinical presentation and management are not well represented in literature. Here, we present a case of profound hyperglycemia and lactic acidosis without hyperammonemia in a propionic acidemia patient, where medical management incorporated mitochondrial dysfunction via a brief reduction in glucose infusion rate. We review the literature on propionic acidemia and mitochondrial dysfunction in an effort to provide a tangible clinical case where considerations of mitochondrial dysfunction were made to guide further decision making in taking care of this patient population.