Summary

Development of gonadal and phenotypic sex during embryogenesis invariably corresponds to the genotypic sex. However, some disorders of sex development are associated with discordance between the chromosomal, gonadal or phenotypic sex which include complete androgen insensitivity syndrome, 46XY complete gonadal dysgenesis (Swyer syndrome) and, rarely, congenital adrenal hyperplasia due to CYP 17A1 (17α-hydroxylase) deficiency. The enzyme CYP17A1 includes 17α-hydroxylase and 17,20-lyase which are required for the synthesis of cortisol and sex steroids, respectively. The consequent cortisol deficiency results in a compensatory increase in adrenocorticotropic hormone (ACTH) drive, which stimulates the production of deoxycorticosterone and corticosterone leading to hypertension and hypokalaemia. Concurrent lack of sex steroids results in sexual infantilism without ambiguity. Both the genotypic males and females present during adolescence with a female phenotype, sexual infantilism and hypertension depending on the severity of the enzyme deficiency. We describe a case of CYP17A1 deficiency in a phenotypic female with 46XY karyotype who presented with sexual infantilism but without hypertension.