Rare forms of congenital adrenal hyperplasia: pathogenesis, clinical, treatment and management

Congenital adrenal hyperplasia (CAH) comprises a group of autosomal recessive disorders caused by numerous variants in several genes encoding enzymes involved in adrenal steroidogenesis. While 21-hydroxylase deficit is the most common and well-known form of CAH, accounting for 90%-95% of cases, there are six other forms of CAH, due to mutations in the genes of other key enzymes involved in adrenal steroidogenesis. These forms are less frequent and, consequently, clinician experience is extremely limited. These disorders are 11β-hydroxylase deficiency (11βOHD); 17α-hydroxylase/17,20-lyase deficiency (17OHD); 3β-hydroxysteroid dehydrogenase type 2 deficiency (3ΒHSD2D); P450 oxidoreductase deficiency (PORD); steroidogenic acute regulatory protein (StAR) deficiency, causing congenital lipoid adrenal hyperplasia and cholesterol side-chain cleavage enzyme (P450scc) deficiency. This narrative review therefore focuses on these rarer forms of CAH, providing an update on their clinical presentation, diagnosis, management, and treatment.