MMADHC and Methylmalonic aciduria: Recently, as ABCD4 and LMBD1 have been shown to interact with the cobalamin processing proteins, methylmalonic aciduria and homocystinuria type C protein and methylmalonic aciduria and homocystinuria type cblD (20), it has been hypothesized that cobalamin might be transported more efficiently by ABCD4 from lysosomes in vivo.