Treatment with thiamine for PDH deficiency may only work with certain pathogenic variants on the thiamine pyrophosphate binding site within the α-subunit of PDH, i.e., p.H44R, p.R88S, p.G89S, p.R263G, and p.V389fs (31, 32). The gene discussed is PDP1; the disease is hyperinsulinemic hypoglycemia, familial, 4.