Carrier frequency of congenital adrenal hyperplasia (21-hydroxylase deficiency) in a middle European population

Based on newborn screening data, the carrier frequency of congenital adrenal hyperplasia (CAH) in the general population has been estimated to be 1:55. The higher CAH frequency (particularly of milder forms of the disease) reported for certain populations including Yugoslavs (1.6%) relates to population genetic and hormonal data. However, so far, true carrier frequency for CAH due to 21-OH deficiency has not been determined by comprehensive mutation analysis of the 21-OH gene (CYP21A2) in an unselected European population. This study used CYP21A2 genotyping (sequence/Southern blot analysis) to determine CAH carrier frequency in a middle European (Austrian) population. The study included 100 migrants from the former Yugoslavia and 100 individuals of non-Yugoslavian origin. None of these individuals showed clinical hyperandrogenism or had a family history of CAH. Genotyping 400 unrelated alleles from 200 clinically unaffected individuals, this study revealed a carrier frequency of 9.5%, including so-called "classic" (5.5%) and "nonclassic" (4%) CYP21A2-gene aberrations. The observed heterozygosity for CAH in Yugoslavs was not different (P = 0.8095) from that in non-Yugoslavs. In conclusion, the observed CAH carrier frequency of 9.5% suggests a higher prevalence of CAH heterozygosity in a middle European population than hitherto estimated independently of the individuals' Yugoslav or non-Yugoslav origin.