Turner syndrome - Genetic syndromes: Patterns of inheritance

Turner syndrome

Definition

Loss of a sex chromosome resulting in a 45,XO genotype.

Incidence

1 in 5000 live births.

Age

Congenital.

Sex

Phenotypically female.

Aetiology/pathophysiology

The commonest underlying karyotype is 45,X; how-ever, many females are mosaics: 45,X/46,XY (other mosaics include 45,X/47,XXX or 45,X/46,XY). There is no increase in incidence with advancing maternal age. Most cases of Turner syndrome spontaneously abort during pregnancy.

Clinical features

During pregnancy there may be generalised hydrops or localised swelling on ultrasound due to late maturation of the lymphatic system. Intrauterine growth retardation is common.

Neonates are phenotypically female, neck webbing, puffy hands, low posterior hairline, large carrying angles (cubitus valgus), wide spaced nipples, and carpal/pedal oedema.

Adults present with infantile genitalia, short stature (<150 cm), wide spaced nipples, neck webbing, micrognathia and prominent ears, wide carrying angle.

Increased frequency of renal (horseshoe kidney) and cardiovascular anomalies (coarctation of aorta) plus mild mental retardation in ∼10%. As there is normally only one copy of the X chromosome, females suffer from X linked recessive conditions such as haemophilia.

Usually normal intelligence and life expectancy, but deficient spatial perception, perceptual motor organisation or fine motor execution.

Investigations

Genetic karyotyping will confirm the clinical diagnosis.

Management

Growth hormone in childhood and oestrogen at puberty allows better growth and the development of secondary sexual characteristics but has no effect on fertility.