Siblings with glutaric aciduria type 1 with atypical phenotype with novel pathogenic variant in GCDH gene

Glutaric aciduria type 1 (GA1) is caused by a deficiency of the enzyme glutaryl CoA dehydrogenase. It generally presents with developmental delay, dystonia, and large head. We are reporting siblings of GA1, presenting with an atypical phenotype with novel pathogenic variant. Thirteen-year-old boy presented with global developmental delay and stiffness of limbs. Examination revealed normocephaly and generalized dystonia. MRI T2WI was suggestive of symmetrical posterior putaminal atrophy. Tandem mass spectroscopy (TMS) and urinary gas chromatography-mass spectrometry (GCMS) were normal. Genetic analysis revealed a novel pathogenic homozygous missense variant in GCDH gene. An 8-year-old girl younger sibling of above child also had developmental delay and dystonia, posterior putamen atrophy in the MRI of brain, and same pathogenic variant in GCDH gene. Parents screening showed heterozygous status in both parents of same pathogenic variant. Any child who presents with global developmental delay with dystonia even with normocephaly, isolated symmetrical posterior putamen changes, with normal TMS and GCMS, a possibility of glutaric aciduria type 1 has to be considered.