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. This evidence concerns the gene LMBRD1 and Methylmalonic aciduria.