In family 8, four affected individuals were found to have a homozygous duplication mutation (c.360dupC; p.Thr121HisfsTer7) in the BCKDK gene (NM_005881.4), which is associated with branched-chain ketoacid dehydrogenase kinase deficiency (OMIM 614923). Here, BCKDK is linked to hyperinsulinemic hypoglycemia, familial, 4.