The identification of 11β-hydroxylase deficiency as a cause of congenital hypertensive hyperandrogenism was first proposed in the 1950 s [16], and accounts for approximately 5% of CAH cases [15]; 11β-hydroxylase is encoded by CYP11B1 on chromosome 8q21 and more than 100 mutations have been described, including chimeric CYP11B1/CYP11B2 forms [17] and uniparental disomy [18], but there appears to be little correlation between genotype and phenotype [19]. The gene discussed is CYP11B1; the disease is congenital adrenal hyperplasia.