Early Onset Methylmalonic Aciduria and Homocystinuria cblC Type With Demyelinating Neuropathy

Methylmalonic aciduria and homocystinuria, cblC type, is the most common inborn error of vitamin B12 (cobalamin) metabolism. The recent cloning of the disease gene, MMACHC, has permitted genotype-phenotype correlation. In a 1-year-old girl, compound heterozygous c.271dupA and c.616C>T mutations in MMACHC were identified as causing an early onset methylmalonic aciduria and homocystinuria, cblC type, which was complicated by sensorimotor peripheral demyelinating neuropathy.