However, 21 patients were diagnosed with methylmalonic acidemia in this study, 52.4% of patients with isolated MMA and 47.6% with combined MMA with homocysteinemia, which were different from most reported conclusions that combined MMA with homocysteinemia caused by the MMACHC gene mutation is the common type of MMA in the mainland of China 26,27. The gene discussed is MMACHC; the disease is methylmalonic acidemia.