Methylmalonic acidemia is an autosomal recessive disorder characterized by the accumulation of methylmalonic acid due to a defect in intracellular cobalamin metabolism (coenzyme deficiency). Some children with this defect may also have simultaneous homocystinuria. The disease presents during the neonatal period or early infancy.

Patients may present hydrocephalus, microcephaly, lethargy, seizures, progressive myopathy, thrombosis and stroke.

Ocular findings include epicanthal folds, nystagmus, retinopathy with conspicuous maculopathy, and reduced visual acuity.

Differential Diagnosis:

• Branched-chain ketoaciduria
• Metabolic acidosis
• Propionic acidemia