LOW-FREQUENCY OF DELETION ALLELES IN PATIENTS WITH STEROID 21-HYDROXYLASE DEFICIENCY IN A MEXICAN POPULATION

Steroid 21-hydroxylase deficiency is caused by mutations in the CYP21 gene. Approximately 95% of mutant alleles are generated by recombinati on events between the acitve gene CYP21 and its highly homologous pseu dogene, CYP21P. Deletion alleles are generated by unequal crossing ove r, while point mutations are the result of gene conversion events. Del etions account for 20-25% of the 21-hydroxylase deficiency alleles in most populations studied. We have looked for deletions among 53 unrela ted Mexican patients with steroid 21-hydroxylase deficiency and found that deletions represent less than 1% of the disease alleles. These fi ndings suggest that nearly all mutant alleles in our patient populatio n contain point mutations and that the low representation of deletion alleles among clinically diagnosed patients may be due to missing dete ction of salt wasters, mainly males, who may die during the neonatal p eriod.