Klinefelter’s syndrome, also known as congenital testicular hypoplasia or primary microcephaly, was first reported by Klinefelter et al. in 1942 and named after Brandbury et al. in 1956, who found an X chromosome in the somatic cells of these patients (normal males are X chromosome negative), and Jacob and Strong et al. in 1959, who confirmed that the patient’s In 1959 Jacob and Strong et al. confirmed that the karyotype of the patient was 47, XXY, so the disease was also called XXY syndrome. 1. incidence and clinical manifestations of Klinefelter syndrome Klinefelter syndrome is mainly manifested as polymorphism of X chromosome and accounts for 0. 1% ~0 .2% of male neonates, 10% of azoospermic males and 5% of severe oligospermia. The most common karyotype in Creutzfeldt-Jakob syndrome is 47, XXY, which accounts for about 80% of Creutzfeldt-Jakob syndrome, and chimeric types account for 15%, including 46, XY/47, XXY, 45, X/46, XY/47, XXY, 46, XX/47, and XXY. Klinefelter syndrome is characterized by tall stature, small and hard testes, and hypoplastic secondary sexual characteristics. The patient has a taller stature, thin bones, relatively long limbs, feminine physical features, sparse beard and pubic hair, small penis, low testosterone, and mild to moderate mental retardation. Usually, adult males present with infertility: azoospermia or severe oligospermia, low testosterone and the resulting symptoms such as erectile dysfunction and low libido. Adolescent males present with genital and pubertal developmental disorders, with a testicular volume of less than 10 ml and a hard texture, and should be further evaluated for penile size, androgen, follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels. It has been shown that patients with Creutzfeldt-Jakob syndrome are more likely to develop extratesticular germ cell-derived tumors and are also susceptible to autoimmune diseases, and that patients with Creutzfeldt-Jakob syndrome are 14 times more likely to develop SLE than normal men.$ 2. Clinical diagnosis Karyotype analysis is the gold standard for the diagnosis of Klinefelter syndrome. For patients with high clinical suspicion of Klinefelter’s syndrome, karyotype analysis is feasible to clarify the diagnosis. However, for low percentage of chimeric Klinefelter syndrome, it is also easy to miss the diagnosis. 3. Prenatal diagnosis Currently, abnormal fetal sex chromosome numbers can be suggested by non-invasive prenatal screening (NIPT). Amniotic fluid cells obtained by amniocentesis can be quickly detected by STR and FISH, but karyotype analysis is still needed to confirm the diagnosis. 4. Treatment Klinefelter syndrome is a chromosomal abnormality and there is no good treatment for it. Some studies have shown that patients with Klinefelter syndrome have spermatogonia at birth, but lose a large number of germ cells during puberty. Therefore, we can only recommend that patients with Klinefelter syndrome should be diagnosed and treated as early as possible. After the diagnosis is confirmed by chromosomal analysis, androgen replacement therapy should be administered during puberty to maintain the male phenotype, improve the patient’s psychology, and enhance the patient’s quality of life, while reserving sperm in advance, the chances of having their own offspring will be greatly increased.$