Recently, Ms. Wang discovered that her 15-year-old daughter not only did not have the breast development and menstrual flow that girls of her age should have, but also had masculine features such as thickened voice, hidden throat knots in the neck, and hairiness. Upon the doctor’s inquiry, Ms. Wang’s daughter was found to have an enlarged clitoris at birth and occasionally felt a lump in her groin area, but did not pay attention to it and had not been formally treated. A thorough examination revealed that Ms. Wang’s daughter’s karyotype was 46,XY, a normal male karyotype; and the mass in the groin was examined by ultrasound as testicular tissue. After further endocrine hormone and genetic testing, it was clear that her disease was called 5α-reductase type 2 deficiency, which is a disorder of conversion of testosterone to dihydrotestosterone and belongs to an autosomal recessive disorder of abnormal sexual development. What is a sexually developmental disorder? In simple terms, what we call “sex” mainly includes chromosomal sex (46,XY in normal males and 46,XX in normal females) and gonadal/expressive sex, such as uterus, ovaries, fallopian tubes, breast development and menstruation during puberty in normal females, and testes, penis and puberty in normal males. low voice, seminal emission, erection, etc. When the chromosomal sex is abnormal (neither 46,XY nor 46,XX) or the chromosomal sex is normal, but there is no corresponding gonad and/or phenotype (e.g., 46,XY but female appearance in the previous case), it is called Disorders of Sex Development (DSD). The causes of DSDs are diverse, but more than 80% of them are due to genetic mutations that cause abnormal hormone levels in the body, resulting in abnormal development of the reproductive system. For example, in male fetuses, the lack of testosterone synthesis or impaired action during development can lead to penile shortening and hypospadias, while in female fetuses, exposure to excessive androgens during development can cause penile enlargement of the clitoris, resulting in blurred external genitalia in newborns. The clinical presentation of patients is also extremely diverse. The external genitalia can be completely male or completely female, and more often the presentation is somewhere between male and female, such as hypospadias, micropenis, cryptorchidism, and clitoral hypertrophy. Among them, hypospadias is an abnormal position of the urethral opening and is one of the most common signs of abnormal sexual differentiation disorders, while clitoral hypertrophy is a condition in which the length and diameter of the clitoris significantly exceeds the normal size. However, due to the complexity of the causes and the lack of knowledge of these diseases in primary hospitals, patients and their families often go around and seek medical help, which seriously affects the quality of life of patients and causes serious physical and mental trauma. With the development of life science and technology, the diagnosis and treatment of abnormal sexual development is now advocated in a multidisciplinary way, with a joint diagnosis and treatment team consisting of endocrinologists, urology, pediatrics, gynecology, genetics, imaging and psychologists. The specific treatment plan is determined by the cause of the disease, the development of the external genitalia, and the wishes of the patient and the patient’s parents. Among them, the clarification of the cause of the disease is the key factor in deciding the treatment plan, which can predict the development of the patient’s disease; and the combination of medication and surgery is the only way to achieve satisfactory treatment results and greatly improve the prognosis of the disease, so that the patient can have a good life as well.