Mutations in the kelch protein interaction domain of HCFC1 cause methylmalonic aciduria with homocystinemia, type cblX (cblX), a multiple congenital anomaly syndrome characterized by abnormal vitamin B12 metabolism, craniofacial dysmorphia, neurodevelopmental defects, failure to thrive, and intractable epilepsy [2]. This evidence concerns the gene HCFC1 and Hyperhomocystinemia.