CYP21A2 and hyperinsulinemic hypoglycemia, familial, 4: This assay is a simple cost-effective technique to genotype point mutations in CYP21A2 gene and to identify junction sites in chimeric genes of CYP21A2 - CYP21A1P rearrangement that contributes to more than 90% of mutations in 21 – hydroxylase deficiency.