A girl with tomboy behavior: lesson from misdiagnosis in a baby with ambiguous genitalia.

5alpha-Reductase-2 deficiency is a rare 46,XY disorder of sex differentiation caused by mutations in the 5alpha-reductase type 2 gene. It presents at birth with variable degree of undervirilization. Here, a baby with 5alpha-reductase-2 deficiency and misdiagnosis of complete androgen insensitivity syndrome, female sex assignment and early gonadectomy is described. During primary school, the girl developed tomboy behavior. Molecular analysis demonstrated compound heterozygosity for 5alpha-reductase type 2 gene mutations (exon 2: Q126R; exon 4: H230P). This child underlines the need for adequate endocrine and genetic testing for a definite diagnosis before gender is assigned in children with ambiguous genitalia and surgical interventions are carried out. Inadequate work-up may result in inappropriate gender assignment in infancy with possible inferences on outcome. Copyright 2009 S. Karger AG, Basel.