XXY chromosome refers to the fact that the patient has a sex chromosome of 47XXY, which is one more X chromosome than normal males. It is clinically known as 47XXY syndrome, also known as Cranfelt’s syndrome or varicocele hypoplasia or primary microtestoidism. Patients usually have no abnormalities in childhood, and in adolescence or adulthood, they may develop a taller body size, elongated lower limbs, fine white skin, scant pubic hair as well as beard, often without axillary hair, and some patients may develop hypertrophy of both breasts. As a result of reduced testosterone production and increased gonadotropin concentration, the penis is shorter than normal males, the testes are significantly smaller, sexual function is poorer, there is no sperm in the semen, and mental development is normal or slightly lower.