The standard diagnostic method is the analysis of the chromosomes' karyotype on lymphocytes. A small blood sample is sufficient as test material. In the past, the observation of the Barr body was common practice, as well. To investigate the presence of a possible mosaicism, analysis of the karyotype using cells from the oral mucosa is performed. Physical characteristics of a<unk>  can be tall stature, low body hair, and occasionally an enlargement of the breast. Usually, a small testicle volume of 1–5 ml per testicle (standard values: 12–30 ml) occurs. During puberty and adulthood, low testosterone levels with increased levels of the pituitary hormones FSH and LH in the blood can indicate the presence of<unk> . A spermiogram can also be part of the further investigation. Often. an azoospermia is present, or rarely an oligospermia. Furthermore,<unk>  can be diagnosed as a coincidental prenatal finding in the context of invasive prenatal diagnosis (amniocentesis, chorionic villus sampling). About 10% of<unk>  cases are found by prenatal diagnosis. The symptoms of<unk>  are often variable, so a karyotype analysis should be ordered when small testes, infertility, gynecomastia, long arms/legs, developmental delay, speech/language deficits, learning disabilities/academic issues, and/or behavioral issues are present in an individual.
Klinefelter syndrome
XYY syndrome
Kallmann syndrome
Turner syndrome
Wilson–Turner syndrome
Angelman syndrome
Parsonage–Turner syndrome
XYYYY syndrome