Low frequency of CYP21B deletions in Brazilian patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

The frequency of large mutations was determined in 131 Brazilian patients w ith different clinical forms of 21-hydroxylase deficiency, belonging to 116 families. DNA samples were examined by Southern blotting hybridization wit h genomic CYP21 and C4cDNA probes after Taql and Bg/II restriction. Large g ene conversions were found in 6.6% and CYP21B deletions in 4.4% of the alle les. The breakpoint in these hybrid genes occurred after exon 3 in 92% of t he alleles, All rearrangements involving CYP21B gene occurred in the hetero zygous form, except in a patient with simple virilizing form who presented homozygous CYP21B deletion. Our data showed that in these Brazilian patient s, CYP21B deletions were less frequent than in most of the large series pre viously reported.