LMBRD1 and hyperinsulinemic hypoglycemia, familial, 4: The mut type and the cblA, cblB, and cblH deficiency types present as MMA alone and are classified as isolated MMA; the cblC, cblD, and cblF deficiency types are classified as MMA combined with homocysteinemia5,6, MMA combined with homocysteinemia is the main biochemical type of MMA in China, accounting for 60–80% of cases7, and cblC is the most common subtype8,9.