[Diffuse hypertrichosis revealing non-classical congenital adrenal hyperplasia]

Non-classical congenital adrenal hyperplasia (NC-CAH) is a recessive autosomal disease caused by a deficiency of adrenal steroidogenesis enzymes. It must be distinguished from classical CAH, either simple virilising or salt-wasting, diagnosed during the neonatal period and responsible for potentially lethal disorders of sexual differentiation. NC-CAH presents a simpler and less specific clinical picture. Herein, we present two cases comprising twin girls consulting for diffuse hypertrichosis.

Two 5-year-old twin girls were seen at our consultation for increased pilosity on all four limbs, but with no facial pilosity or synophrys, as well as comedones on the chin. Their height and weight and psychomotor development was normal, with no signs of precocious puberty and no clitoral hypertrophy. Levels of 17OH-P and SDHA were high, while FSH and LH were low and IGF1 and TSH were normal. Analysis of gene CYP21 associated with NC-CAH showed mutations p.V281L and IVS2-13A/C>G. Mutation p.V281L was present in the heterozygous state in the older sister and the father, together with moderate hyperpilosity but without hirsutism or acne. No mutations were found in the mother, indicating either de novo appearance of mutation IVS2-13A/C>G in the twins or germline mosaicism in the mother.

We diagnosed NC-CAH as the cause of diffuse hypertrichosis in these twins. This disease is not rare, with a prevalence of 1/1000 to 1500 among peoples of European descent. It is often diagnosed late since routine neonatal screening is not performed. In some cases, NC-CAH remains asymptomatic. The appearance of pubic hair at around 5 to 7 years is the initial reason for consultation, particularly with a dermatologist. Hyperandrogenism varies, involving hirsutism, acne, fertility disorders and premature ageing of bone. Cortisol and aldosterone levels are generally normal. The risk of acute adrenal insufficiency is extremely low. Differential diagnosis concerns ovarian or adrenal tumors and polycystic ovary syndrome. 21-OH deficiency results in defective cortisol and aldosterone synthesis, and thus in raised ACTH, leading to increased adrenal androgen secretion. The early appearance of secondary sexual characteristics is associated with a gradual accumulation of 17-OHP. Depending on severity, hydrocortisone or anti-androgens may be given, or where treatment fails, aesthetic measures such as epilation or hair discolouration may be performed.

In children presenting NC-CAH, the appearance of pubic hair and hirsutism often constitute the initial reasons for consultation, including with dermatologists. However, hypertrichosis may occur in isolation. It is important that these abnormalities be clearly known to enable early diagnosis and rapid initiation of simple and readily accessible treatment.