Lipoid Congenital Adrenal Hyperplasia - Genetics and Epidemiology

Genetics and Epidemiology

This inherited disease is autosomal recessive. Understanding of the molecular basis for it has been advanced in the last decade by better understanding of adrenal steroidogenesis as well as genetic studies of affected patients. It used to be assumed that lipoid CAH resulted from a defect of the enzyme that converted cholesterol to pregnenolone. The conversion reactions are mediated by a single enzyme, formerly referred to as 20,22-desmolase, but now identified as cytochrome P450scc (cholesterol side chain cleavage enzyme). However, few cases of lipoid CAH due to a mutation and defect of P450scc have been identified. Although the disorder is considered autosomal recessive, a single mutation in P450scc can be sufficient to cause the condition. All other cases of lipoid adrenal hyperplasia that have been studied have been found to be due to mutations of the gene for the primary protein that transports cholesterol into the mitochondria, StAR, encoded by a gene on chromosome 8p11.2 in the human.

Lipoid CAH is quite rare in European and North American populations. Most cases occur in Japan and Korea (where the incidence is 1 in 300,000 births) and Palestinian Arabs. Despite autosomal inheritance, there has been an unexplained preponderance of genetic females in reported cases.