Disability/Illness Description:

Klinefelter Syndrome (KS) is a birth defect in which males are born with at least one extra sex chromosome. In 1942, certain physical characteristics, abnormal in adult males, were first identified by Dr. Harry Finch Klinefelter, Jr. and two colleagues. These characteristics were abnormally small testes and fatty breast tissue. Detailed chromosome studies conducted years later resulted in the discovery that males with these characteristics have an extra sex chromosome


American Association for Klinefelter Syndrome Information and Support – AAKSIS (pronounced “access”)
AAKSIS is dedicated to bringing you accurate and current information about Klinefelter Syndrome and is a network for individuals, families, and anyone interesting in learning more about Klinefelter Syndrome.
2945 W. Farwell Ave.
Chicago, IL 60645-2925
Phone: 888 466-5747

P.O. Box 861
Mendenhall, PA 19357
Phone: 888-999-9428
Fax: Please send your document as an email attachment
Email: info@genetic.org
Family Information Kits

Klinefelter Syndrome Information and Support
Living with Klinefelter Syndrome, links to other organizations, support groups and resources.
* Steps for Starting a Support Group

Other Information:

Kleinfelter’s Syndrome –  Genetics Home Reference US National Library of Medicine

Klinefelter Syndrome – National Institute of Health

Fact Sheet last updated on: 4/10/2020