A rare enzymatic defect, true isolated 17,20-lyase deficiency leading to endocrine disorders and infertility: case report.

The cytochrome P450 17A1 catalyzes the formation of 17-hydroxysteroids and 17-ketosteroid. Most defects in CYP17A1 impair both enzymatic activities and cause a combined 17α-hydroxylase/17,20-lyase deficiency, which impairs hormone production (cortisol and sex steroids), sexual development, and puberty. Isolated 17,20-lyase deficiency is usually defined by evidently normal activity of 17α-hydroxylase with a dramatic decline of 17,20-lyase activity or complete inactivity. The changes in enzyme activity lead to a lack in the production of sex steroids with normal levels of glucocorticoid and mineralocorticoid hormones. A 24-years-old married woman, as a product of a consanguineous marriage, presented with infertility and a background marked by primary amenorrhea. Laboratory data showed low normal serum cortisol levels and low levels of 17-hydroxyprogesterone. Also, her adrenal androgens were low but estradiol was normal. The chromosomal investigation uncovered a male karyotype of 46, XY. These clinical and laboratory evidence confirm the determination of an isolated 17,20-lyase deficiency in a genotypic male.