MMUT and homocystinuria: Of these 13 MMA cases, seven were isolated MMA, and among them, six were caused by variants in MMUT and one was caused by a variant in MCEE. The other six cases were MMA with homocystinuria, which was caused by variants in MMACHC. We found six novel variants in three MMA-causing genes as follows: c.2008G>A, c.301_302insTA, c.984delC, and c.319A>T of MMUT; c.445T>C of MMACHC; and c.296T>C of MCEE. We provided prenatal diagnosis for two families with MMA at their next pregnancy, and one family had a healthy newborn.