Mt. Tusieluna et al., LOW-FREQUENCY OF DELETION ALLELES IN PATIENTS WITH STEROID 21-HYDROXYLASE DEFICIENCY IN A MEXICAN POPULATION, Human genetics, 98(3), 1996, pp. 376-379
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.