CYP19A1 and hyperinsulinemic hypoglycemia, familial, 4: Based on the clinical history, we suspected aromatase deficiency and Sanger sequenced the nine coding exons of CYP19A1. We also sequenced the coding exons of P450-oxidoreductase (POR), the electron donor for cytochrome P450 enzymes (including CYP19A1), which has been associated with a phenotype of ambiguous genitalia and, via consequent dysfunction of CYP19A1, could result in maternal virilisation in pregnancy [26].