For example, among the 19 diseases with ‘Ketosis’ as clinical sign, two of them were classified as oligogenic: maple syrup urine disease with 3 genes (BCKDHA, BCKDHB and DBT) and Permanent neonatal diabetes mellitus with 4 genes (GCK, INS, KCNJ11 and ABCC8). The gene discussed is BCKDHB; the disease is maple syrup urine disease.