HLA typing and ACTH stimulation in the detection of carriers for 21-hydroxylase deficiency.

Two methods of carrier detection were applied to the siblings of two children with congenital adrenal hyperplasia due to 21-hydroxylase (21-OH) deficiency. HLA geno-typing showed that the affected children were HLA identical. One of the siblings possessed only one of the relevant haplotypes, and was shown to be heterozygous for 21-OH deficiency by the 17 alpha hydroxyprogesterone response to ACTH stimulation. The other sibling had a maternal recombination between the DR and glyoxylase-1 (GLO) loci. The ACTH stimulation test was normal and therefore confirms recent reports suggesting that the 21-OH gene is between the HLA-A and the GLO loci. Although HLA typing of family members will identify heterozygous 21-OH deficiency in most instances, biochemical definition is still required for some cases with recombinations in the short arm of chromosome 6.