Methylmalonic Acidemia With Homocystinuria, Type Cblc

cblC type methylmalonic acidemia with homocystinuria is a form of methylmalonic acidemia with homocystinuria (see this term), an inborn error of vitamin B12 (cobalamin) metabolism characterized by megaloblastic anemia, lethargy, failure to thrive, developmental delay, intellectual deficit and seizures.

Epidemiology

To date, over 500 cases of cblC have been reported, making it the most frequent type of methylmalonic acidemia with homocystinuria.

Clinical description

The disease typically presents with failure to thrive, acute neurological deterioration, intellectual deficit, lethargy, seizures, microcephaly, a salt-and-pepper retinopathy, and signs of megaloblastic anemia (pallor, fatigue, anorexia). Severe brain abnormalities including hydrocephalus, white matter abnormalities, cerebral atrophy, and unusual basal ganglia lesions are common. Onset of the disorder can be early (infantile) or late (juvenile or adult), with the late-onset form characterized by ataxia, dementia and psychosis.

Etiology

cblC type methylmalonic acidemia with homocystinuria is caused by mutations in the MMACHC gene (1p36.3) and is transmitted in an autosomal recessive manner.