[Virilizing congenital adrenogenital syndrome with a de novo I172N mutation: study of a new case]

The classical form of congenital adrenal hyperplasia is the result of mutations in the 21-hydroxylase gene (CYP21A2). Most deficient alleles carry pre-existing mutations in the CYP21PA homologue pseudogene, located in tandem. Mutant alleles are inherited from carrier parents, and de novo mutations during gametogenesis or foetal development are exceptional. The present paper describes a de novo mutation occurring at the maternal allele (I172N) of a patient with a classical form of 21-hydroxylase deficiency, whose father was heterozygous for R356W. The mother did not carry the mutation. Microsatellite analyses confirmed a correct allelic segregation. The I172N mutation (in compound heterozygosity with a null mutation) gives rise to a virilizing phenotype not associated with salt-wasting.