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 B 12 (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.