Turner's Syndrome (45, X)

Original article by Tom Leach | Last updated on 7/6/2014
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Introduction

In this condition there is only one X chromosome in the female.

 

Epidemiology

  • 95% of cases result in spontaneous miscarriage
  • Present in 1 in 5000
 

Clinical features

Vary widely from case to case. Some cases may be very mild, and typically in these individuals the only apparent sign is short stature. Presentation can be anywhere from the fetal stage (usually second trimester via USS) to adult life.

Fetus

  • Generalised oedema (hydrops)
  • Nuchal thickening / fat pad

Neonates

  • Many appear completely normal
  • Peripheral oedema
  • Webbed neck
  • Low posterior hairline
  • Shortening of the 4th metacarpal
  • Nipples widely spaced
  • Coarctation of the aorta

Neurological signs

  • Intelligence is normal
  • Social skills and some other high functional skills may be altered
  • The bell curve for IQ is thought to be slightly to the left

Late signs

  • Short stature – usually seen in childhood from age 5 onwards. Growth hormone therapy can help reduce the deficit. Without therapy, the average height is 145cm.
    • this is thought to be related to a lack of the SHOX gene
  • Ovarian defects – often resulting in infertilityPregnancy is still possible with IVF and donated ova.
  • Hypothyroidism
  • Pigmented moles
  • Wide carrying angle of the arm
  • Recurrent otitis media
  • Delayed puberty
 

Treatment

  • Growth hormones to avoid short stature
    • Offered from the age of 3 onwards
    • No good if epiphyseal plates have already fused
  • Oestrogen at pubertal age to ensure development of secondary sexual characteristics. Infertillity still usually persists. 
 

Cytogenet​ics

  • 50% of cases are (45,X)
  • In 80% of these cases the defect is due to the loss of either an X or Y during paternal meiosis.
  • In most other cases, there is deletion of part of or all of one of the arms of chromosome X.
  • in some cases, there is considerable mosaicism, and thus there is a normal cell line in many of the patient’s cells (46, XX). These patients have a good chance of being fertile