Diseases

Klinefelter Syndrome

A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).

National Library of MedicineMedical Subject Headings2026

Structured Summary

Abstract

A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).

MeSH Record

Classification

Broader headings

Related Concepts

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MeSH Record

Synonyms

26 entry terms
  • Klinefelter's Syndrome
  • XXY Syndrome
  • Klinefelter Syndromes
  • Klinefelters Syndrome
  • Syndrome, Klinefelter
  • Syndrome, Klinefelter's
  • Syndrome, XXY
  • Syndromes, Klinefelter
  • Syndromes, XXY
  • XXY Syndromes
  • 48,XXYY Syndrome
  • 49,XXXXY Syndrome
  • Klinefelter Syndrome, Variants
  • XXXY Males
  • XXY Trisomy
  • Xxyy Syndrome
  • Klinefelter Syndromes, Variants
  • Syndrome, Variants Klinefelter
  • Syndrome, Xxyy
  • Syndromes, Variants Klinefelter
  • Syndromes, Xxyy
  • Trisomies, XXY
  • Trisomy, XXY
  • XXXY Male
  • XXY Trisomies
  • Xxyy Syndromes

MeSH Record

Aspects Covered

34 allowable subheadings

Indexed with the subheadings blood, cerebrospinal fluid, chemically induced, classification, complications, diagnosis, diagnostic imaging, diet therapy, drug therapy, economics, embryology, enzymology, epidemiology, ethnology, etiology, genetics, history, immunology, metabolism, microbiology, mortality, nursing, parasitology, pathology, physiopathology, prevention & control, psychology, radiotherapy, rehabilitation, surgery, therapy, urine, veterinary, virology.

MeSH Record

Indexing Annotation

index here karyotypes XXXY, XXXXY, XXYY, XXXYY, XX/XXY, XX/YY, XY/XXY, XXY/XXXY, XXY/XXYY, XY/XXY/XXXY if called KLINEFELTER SYNDROME by author but if not so named by author, index under SEX CHROMOSOME DISORDERS

MeSH Hierarchy

Tree Numbers

  1. C12.050.351.875w.253w.795.500w
  2. C12.200.706w.316w.795.500w
  3. C12.800w.316w.795.500w
  4. C16w.131w.260w.830w.835.500w
  5. C16w.131w.939w.316w.795.500w
  6. C16w.320w.180w.830w.835.500w
  7. C19w.391.119w.795.500w
  8. C19w.391.482w.629w

MeSH Record

NLM Classification

QS 677

AMA Style

References

  1. National Library of Medicine. Klinefelter Syndrome. Medical Subject Headings (MeSH). 2026. Unique ID D007713. http://id.nlm.nih.gov/mesh/2026/D007713
  2. Klinefelter Syndrome. In: Wikipedia. https://en.wikipedia.org/wiki/Klinefelter_syndrome
  3. Klinefelter Syndrome. In: Wikidata. https://www.wikidata.org/wiki/Q207133