Methylmalonic acidemia with homocystinuria

Methylmalonic acidemia with homocystinuria is a metabolic disease due to a congenital defect in vitamin B12-cobalamin metabolism. The cobalamin disorders are differentiated into four complementation classes (cblC, cblD, cblF and cb1J).

The first symptoms can occur in all age groups, the prognosis being the more favorable the later the first symptoms appear.

The cause is a synthesis disorder of methylcobalamin and adenosylcobalamin. This is due to the mutation of the genes MMACHC (1p36.3, cblC), MMADHC (2q23.2 cblD), LMBRD1 (6q13 cblF) and ABCD4 (14q24 cblJ), depending on the corresponding complementation class. The mode of inheritance is autosomal recessive or X-linked recessive.