Partial deficiency of 17α-hydroxylase: a rare cause of congenital adrenal hyperplasia.

Congenital adrenal hyperplasia (CAH) due to 17α-hydroxylase deficiency, a rare CAH syndrome, is characterised by failure to synthetise cortisol, adrenal androgens and gonadal steroids. The partial deficiency is much rarer, presenting with subtler symptoms. Failure to reach a proper diagnosis causes inappropriate hypertension treatment and impairs the development of secondary sexual characteristics. We report a case of a 30-year-old woman transferred to an endocrinology clinic for evaluation of autoimmune thyroiditis. She was started on oral contraceptives at the age of 13 due to oligomenorrhea and presented underdeveloped pubic and axillar hair and Tanner stage 3 breast development. Biochemical tests evidenced very low androgens levels and genetic analysis confirmed a CAH due to 17α-hydroxylase deficiency. Partial 17α-hydroxylase deficiency is a rare clinical entity, nevertheless, it should be included in the differential diagnosis of menstrual disorders. © BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.