A novel CYP11B1 mutation in a Turkish patient with 11β-hydroxylase deficiency: An association with the severe hypokalemia leading to rhabdomyolysis.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by the loss of one of five steroidogenic enzymes affecting cortisol synthesis. Deficiency of 21-hydroxylase is the most common cause of CAH, accounting for more than 90% of all cases; it is followed in frequency by 11β-hydroxylase deficiency (11βOHD), reported to be between 3% and 5% of cases.1 Kelestimur et al found that, based on 11-deoxycortisol response to ACTH stimulation, 6.5% of hirsute women in a Turkish population had 11βOHD.2 The 11β-hydroxylase gene is located on chromosome 8q21-q22. In 11βOHD, 11-deoxycortisol cannot be converted to cortisol, and deoxycorticosterone (DOC) cannot be converted to corticosterone. Enzyme inhibition stimulates ACTH secretion resulting in excess androgen and DOC. DOC, which is a less potent mineralocorticoid, causes hypokalemia and hypertension. Two thirds of 11βOHD cases have hypertension. In the classical form of 11βOHD, hypertension in both sexes, ambiguous genitalia in women and increased penile length with normal external genitalia and gynecomastia in men are observed.1 We present a case of 11βOHD with severe hypokalemia and in which we have found a novel mutation.