A partial recessive model with no recombination between 21-OHD and HLA-B fitted the data better than did a complete recessive model with approximately 0.5% recombination between 21-OHD and HLA-B.
We confirm that late-onset of 21OHD is an autosomal recessive disease linked to HLA-B; there is in fact biochemical evidence of mild 21OHD in patients and in their HLA identical sibs and 17-hydroxyprogesterone levels in the range of heterozygotes for classical 21OHD in parents and sibs predicted by HLA to be carriers.
Here, we have used HLA-B genotype data in families containing multiple members affected with nonclassical 21-hydroxylase deficiency together with the results of quantitative hormonal tests to arrive at estimates of gene and disease frequencies for this disorder.
The 21-hydroxylase deficiency is genetically linked to the human leukocyte antigen (HLA) complex; in addition, nonclassical and classical 21-hydroxylase deficiency have each been shown to be in genetic linkage disequilibrium with specific HLA-B antigens.
The hormonal and genetic linkage studies indicate that the late-onset (symptomatic) form of 21-hydroxylase deficiency, like the cryptic (asymptomatic) and classical forms of 21-hydroxylase deficiency, is transmitted by an autosomal recessive gene which is linked to HLA-B.