Each of these disorders is the result of rare autosomal recessive mutations. 3b-HSD deficiency usually results in salt wasting; variable deficiency of the enzyme in the adrenal and liver may complicate diagnosis. 17a-hydroxylase and 17,20-lyase reactions are mediated by a single enzyme, P450l7a, and it is not known why some patients have selective impairment of one enzymatic function. 17a-hydroxylase deficiency results in hypokalaemic alkalosis and hypertension, in addition to gonadal deficiency. 17b-HSOR deficiency is probably the most common of the defects. The external phenotype is usually female, but inguinal or abdominal testes and virilised Wolffian duct structures are present. At the time of expected puberty, both virilisation (phallic enlargement and facial hair growth) and some feminisation (appearance of gynaecomastia) take place.
