[21-Hydroxylase deficiency. Clinical expression of heterozygote carriers in a family].

The observation of a neonate who presented with congenital adrenal hyperplasia due to 21-hydroxylase deficiency and of her aunt who presented with primary amenorrhea and hirsutism led to the genetic study of this family. The ACTH stimulation test and HLA typing proved that the young woman was heterozygous for the C-21 block and that the niece presented with the homozygous condition. This case confirms that, in rare cases, the clinical expression of C-21 block may appear in heterozygous carriers.