由5α-还原酶缺乏所致男性假两性畸形是一种罕见的常染色体隐性遗传病，近年我院收治1例成年患者，现报道如下。患者26岁，社会性别女，未婚。因原发性闭经，外阴发育异常于1991年2月入院。足月顺产，出生后一直接女孩抚养，智力佳，体力强。在小儿生长期；家长发现“大阴唇” Caused by the lack of 5α-reductase Male pseudohermaphroditism is a rare autosomal recessive disease in our hospital admitted to an adult patient in recent years, are reported below. Patient 26 years old, female gender, unmarried. Due to primary amenorrhea, vulvar dysplasia in February 1991 admitted. Full-term follow-up birth, the girl has been raised after birth, good intelligence, physical strength. In the growth of children; parents found that “labia majora”