HLA Typing and ACTH Stimulation in the Detection of Carriers for 21‐Hydroxylase Deficiency*

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Abstract
Summary: 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 77α 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.