Molecular genotyping in Brazilian patients with the classical and nonclassical forms of 21-hydroxylase deficiency

Abstract

The aim of our study was to determine, by allele-specific PCR, the frequency of point mutations in 130 Brazilian patients with the classical and nonclassical forms of 21-hydroxylase deficiency and to correlate genotype with phenotype. The most frequent mutations were 12 splice (41.8% in salt wasting), I172N (32.6% in simple virilizing), and V281L (40.2% in late onset form). The frequency of the 9 most common point mutations was similar to that reported for other countries, except for Del 8 nt and Cluster, which were less frequent in the classical form. Rarer mutations such as P453S, G291S, I7 splice, W405X, R483P, and R483-->frameshift were rarely found or were absent. The 93 fully genotyped patients were classified into 3 mutation groups, based on the degree of enzymatic activity (group A, <2%; group B, approximately 2%, and group C, >18%). In group A, 62% of the cases presented the salt wasting form; in group B, 96% the simple virilizing form; and in group C, 88% the late onset form. We diagnosed 80% of the affected alleles after screening for large rearrangements and 15 point mutations. The absence of previously described mutations in 20% of the affected alleles suggests the presence of new mutations in our population.