Spectrum of the genital appearance with 21-hydroxylase deficiency and its classification according to Prader et al. (26). Minimal virilization of the female external genitalia starts with enlargement of the clitoris (Prader 1). With more severe forms the labia majora start fusing from the perineum (Prader 2), forming a combined urogenital sinus with a higher degree of virilization (Prader 3). The extreme is a complete male appearance of the external genitalia with the urethra ending on the tip of the phallus (Prader 5). (Adapted with permission from Riepe et al., Adrenogenitales Syndrom in Rationelle Diagnostik und Therapie in Endokrinologie, Diabetologie und Stoffwechsel. Georg Thieme Verlag, Stuttgart, Germany (35).)