FFinalistSouthampton · 2027
Child health
AKT · Child health/Genetic syndromeslow yield

Klinefelter syndrome

47,XXY (male)

Overview

An extra X chromosome (47,XXY) in males, causing primary hypogonadism — tall stature, small firm testes, gynaecomastia and infertility, often diagnosed at puberty or during infertility work-up.

Recognise

  • TALL stature, long limbs
  • Small firm testes, reduced secondary sexual hair, gynaecomastia
  • Infertility (azoospermia); mild learning/behavioural difficulties

Red flags

  • Increased risk of breast cancer (gynaecomastia), osteoporosis, venous thromboembolism

Differentials & how to tell them apart

Constitutional tall staturenormal karyotype, normal testes/fertility
Marfan syndrometall with lens/aortic features, normal karyotype
Kallmann syndromeLOW LH/FSH (hypogonadotropic) + anosmia

Investigations

Karyotype 47,XXY. Hormones: LOW testosterone with HIGH LH/FSH (hypergonadotropic hypogonadism).

Management

  1. 1Confirm karyotype. Testosterone replacement for hypogonadism; address gynaecomastia and bone health.
  2. 2Fertility counselling/assisted reproduction; psychological/educational support.
Testosterone replacement — for hypogonadism (not fertility)

Key points

Hormone profile is the discriminator: high LH/FSH + low testosterone (primary), vs Kallmann’s low gonadotrophins + anosmia (secondary).

Monitor & prognosis

Testosterone, bone density, breast (cancer risk), metabolic.

Good with replacement; infertility usual.

Source: Clinical genetics