[Genetics of congenital adrenal hyperplasia caused by steroid-21-hydroxylase deficiency: present-day aspects].

Congenital adrenal hyperplasia caused by a deficiency of 21-hydroxylase is an inherited disorder of adrenal steroidogenesis. In this study, the deficiency incidence is presented according to different author's and countries' results. Nowadays knowledge concerning its genetics are reviewed, especially HLA linkage. Allelic variants of deficiency and the "linkage disequilibrium" with HLA complete antigens are described. Finally, the main applications of that knowledge are presented: heterozygote detection and prenatal diagnosis.