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Glutaric aciduria type 1 (GA1) is a rare inherited metabolic disorder caused by a deficiency of glutaryl-coenzyme A dehydrogenase (GCDH), with accumulation of neurotoxic metabolites, resulting in a complex movement disorder, irreversible brain damage, and premature death in untreated individuals. While early diagnosis and a lysine restricted diet can extend survival, they do not prevent neurological damage in approximately one-third of treated patients, and more effective therapies are required. Here we report the efficacy of adeno-associated virus 9 (AAV9)-mediated systemic delivery of human GCDH at preventing a high lysine diet (HLD)-induced phenotype in Gcdh−/− mice. Neonatal treatment with AAV-GCDH restores GCDH expression and enzyme activity in liver and striatum. This treatment protects the mice from HLD-aggressive phenotype with all mice surviving this exposure; in stark contrast, a lack of treatment on an HLD triggers very high accumulation of glutaric acid, 3-hydroxyglutaric acid, and glutarylcarnitine in tissues, with about 60% death due to brain accumulation of toxic lysine metabolites. AAV-GCDH significantly ameliorates the striatal neuropathology, minimizing neuronal dysfunction, gliosis, and alterations in myelination. Magnetic resonance imaging findings show protection against striatal injury. Altogether, these results provide preclinical evidence to support AAV-GCDH gene therapy for GA1.

We report an 8-year-old patient with glutaric aciduria type 1 associated with compound heterozygous mutations c.1204C>T (p.Arg402Trp) and c.547C>T (p.Ser216Leu) in GCDH. Clinical case illustrates the difficulty in diagnosing this hereditary disease, its mimicry of neonatal hypoxic-ischemic encephalopathy and cerebral palsy. The timeliness of early diagnosis and initiation of specific therapy makes it possible to improve the condition of patients.

Abstract Case Description A 9‐month‐old intact male domestic shorthair cat was evaluated for increasing frequency of generalized tonic‐clonic seizures. Clinical Findings The cat was reported to have had episodes of circling between the seizures. Upon examination, the cat had bilateral inconsistent menace response but otherwise normal physical and neurological examinations. Diagnostics Magnetic resonance imaging (MRI) of the brain identified multifocal, small, rounded intra‐axial lesions within the subcortical white matter containing fluid with similar characteristics as cerebrospinal fluid. Evaluation of urine organic acids showed increased excretion of 2‐hydroxyglutaric acid. An XM_023255678.2:c.397C>T nonsense variant in the L2HGDH gene encoding L‐2‐hydroxyglutarate dehydrogenase was identified using whole genome sequencing. Treatment and Outcome Levetiracetam treatment was initiated at 20 mg/kg PO q8h, but the cat died after a seizure 10 days later. Clinical Relevance We report the second pathogenic gene variant in L‐2‐hydroxyglutaric aciduria in cats and describe for the first time multicystic cerebral lesions on MRI.

In humans, a single enzyme 2-aminoadipic semialdehyde synthase (AASS) catalyses the initial two critical reactions in the lysine degradation pathway. This enzyme evolved to be a bifunctional enzyme with both lysine-2-oxoglutarate reductase (LOR) and saccharopine dehydrogenase domains (SDH). Moreover, AASS is a unique drug target for inborn errors of metabolism such as glutaric aciduria type 1 that arise from deficiencies downstream in the lysine degradation pathway. While work has been done to elucidate the SDH domain structurally and to develop inhibitors, neither has been done for the LOR domain. Here, we purify and characterize LOR and show that it is activated by alkylation of cysteine 414 by N-ethylmaleimide. We also provide evidence that AASS is rate-limiting upon high lysine exposure of mice. Finally, we present the crystal structure of the human LOR domain. Our combined work should enable future efforts to identify inhibitors of this novel drug target.

Hemophagocytic lymphocytosis (HLH) is a rare disease caused by inborn errors of immunity (IEI), secondary to infection, lymphoma or autoimmune disorders, but we often overlook the fact that HLH can be secondary to inborn errors of metabolism (IEM). Here, we describe a patient who was diagnosed with glutaric aciduria type IIC complicated by features suggestive of possible HLH. The diagnosis of glutaric aciduria type IIC, a IEM, was confirmed by whole exome sequencing. The patient was treated with coenzyme Q10 and riboflavin which effectively improved her liver function. During treatment, the patient developed severe anemia and thrombocytopenia. Persistent fever, splenomegaly, cytopenias, increased ferritin, hypertriglyceridemia, hypofibrinogenemia, and hemophagocytosis in the bone marrow pointed to the diagnosis of HLH; however, the patient eventually died of gastrointestinal bleeding. After other potential causes were ruled out, the patient was diagnosed with glutaric aciduria type IIC complicated by features suggestive of possible HLH. When cytopenias occurs in IEM patients, HLH is a possible complication that cannot be ignored. This case suggests a possible relationship between IEM and risk for immune dysregulation.

Glutaric aciduria type I (GA1) is an inherited metabolic disorder in which excessive levels of the amino acids lysine, hydroxylysine, and tryptophan accumulate in the body as a result of defective glutaryl-CoA dehydrogenase (GCDH) enzyme activity. Excessive metabolites are toxic that can cause damage to the brain, particularly due to the occurrence of basal ganglia and intellectual disability. Missense, splicing, and other deletion mutations in GCDH gene lead to the deficiency of the enzyme activity and are known to cause GA1. The severity of GA1 along with its neurological manifestations and clinical outcome is dependent upon the age at onset and therefore, early definitive diagnosis of GA1 becomes essential. GA1 occurs in approximately 1 of every 30,000-40,000 individuals worldwide that may reach up to 1 in 300 newborn babies in the Amish and Canadian communities. Owing to very high consanguinity rates in Saudi Arabia, it is presumed to be much more common in the Kingdom and is one of the initial disorders that were included in the country's neonatal screening program. In the current study, we have reviewed clinical manifestations, diagnosis, updated management, and mutation spectrum in GA1 with an example of one of our patients with GA1, and highlighted the importance of multipara-metric strategy in the early diagnosis and management of the disease. [JBCGenetics 2019; 2(1.000): 40-53]

The aim of this study was to determine the key MRI findings in different disease causing macrocrania in early childhood that will help in early detection and diagnosis. Patients and methods: This study was conducted on 20 patients (their age ranged from 3.5 months to 5 years) referred to the radiodiagnosis department in the period between February 2013 and June 2014. All patients were subjected to conventional MRI. MRS was done in 8 cases using PRESS 3D multi-voxel chemical shift imaging. Results: The patients subdivided into 7 groups. Glutaric aciduria type 1 (40%) MRI showed wide operculum sign; MRS done in 4 patients showed elevated choline with preserved NAA peak. Benign macrocrania of infancy (15%), and MRI showed enlarged cranio-cortical and inter-hemispheric subarachnoid spaces beyond 5 mm, mildly dilated ventricles. Van der Knaap disease (15%) showed bilateral symmetrical confluent white matter dysmyelination with bilateral fronto-temporal subcortical cystic changes .MRS done in 2 patients showed increase in Cho/NAA ratios. Mucopolysaccharidosis (10%) showed dilated Virchow Robin spaces. MRS done in one patient showed decreased NAA, and increased choline/creatine ratio. Canavan disease (10%) MRI showed bilateral symmetrical extensive white matter dysmyelination. MRS showed markedly elevated NAA. Alexander disease (5%) showed bilateral symmetrical white matter dysmyelination with frontal predilection. MRS revealed increased NAA/Cr, increased myo-inositol/Cr, and lactate doublet. Gangliosidosis (5%) MRI showed bilateral symmetrical T2 and FLAIR hyperintense putamen. CT showed bilateral symmetric thalamic hyperdensities. Conclusion: MRI can diagnose different causes of non hydrocephalic macrocrania. MRS is helpful in differentiating benign macrocrania of infancy from dysmyelinating diseases and is specific in Canavan Disease.

Glutaric aciduria (GTA) type II can be seen as late onset form with myopathic phenotype. We present a case of a 19-year old female with progressive muscle weakness was admitted in intensive care unit (ICU) with respiratory failure and acute renal failure. Patient was unconscious. Pupils were anisocoric and light reflex was absent. She had hepatomegaly. The laboratory results showed a glucose level of 70 mg/dl and the liver enzymes were high. The patient also had hyponatremia (117 mEq/L) and lactate level of 3.9 mmol/L. Tandem MS and organic acid analysis were compatible with GTA type II. Carnitine 1gr, riboflavin 100 mg and co-enzymeQ10 100 mg was arranged. After four months from beginning of treatment tandem MS results are improved. Respiratory failure, acute renal failure due to profound proximal myopathy can be due to glutaric aciduria type II that responded rapidly to appropriate therapy.