Attenuated forms of congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

A variety of mild forms of congenital adrenal hyperplasia (CAH) due to partial 21-hydroxylase deficiency have recently been described. We report two families in whom members presented with CAH with various degrees of enzyme deficiency. In family A, two children had the classical salt-losing CAH. Their male sibling and mother presented a very mild asymptomatic form of CAH, characterized by elevated basal plasma levels of 17-hydroxyprogesterone (17-OHP) and exaggerated responses of progesterone and 17-OHP to ACTH stimulation. The Hormonal profile and HLA types of these two individuals suggested allelic compounds, having one mutant gene for classical CAH and another for a mild form. In family B, the proband presented an attenuated form of CAH, manifested by amenorrhea and hirsutism, elevated basal levels of plasma 17-OHP and androgens, as well as markedly increased ACTH response. Two of her four siblings had the same ad HLA type, elevated basal plasma 17-OHP levels, and increased ACTH response. Their father, their paternal aunt, and their paternal uncle had the ab HLA type and normal basal plasma 17-OHP but markedly increased ACTH response. The haplotypes a, b, and d were considered to be linked to a mutation resulting in mild 21-hydroxylase deficiency, the homozygotes with ab HLA type having a milder form of CAH than the homozygotes with the ad HLA type. The wide spectrum of clinical and hormonal characteristics among homozygotes for the 21-hydroxylase deficiency trait suggests that their is a continuum of degree of enzyme deficiency. Furthermore, it suggests that most nonclassical subjects are allelic compounds for variable degrees of severity in the mutation at the 21-hydroxylase locus. More specifically, the study of families A and B shows that the so-called cryptic and attenuated forms of CAH have the same pathophysiological basis.