Therefore, isolated 17,20-lyase deficiency is a syndrome, which may be caused by specific mutations in the CYP17A1 (p.R347H, p.R347C, p.R358Q, and p.E305G), POR (p.G539R), and CYB5A (p.W27X and p.H44L) (14). This evidence concerns the gene CYP17A1 and hyperinsulinemic hypoglycemia, familial, 4.