46,XY karyotype and female phenotype were detected in a fetus; 5伪-reductase and androgen receptor gene analysis on chorionic villi revealed no relevant mutation. The newborn was assigned to female sex. The diagnosis of 17尾-hydroxysteroid dehydrogenase-3 尾-OL deficiency was reached at four months of age, by means of a low testosterone/螖 4-androstenedione ratio after HCG test and HSD17B3 gene analysis.
A 46,XY fetus with female external genitalia suggests different conditions, some very rare. Specific genetic investigations should be performed prenatally when possible. A complete evaluation is mandatory after delivery to reach a correct diagnosis.