Turner Syndrome

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Basics

Description

Presence of typical findings in a phenotypic female with complete or partial absence of the second sex chromosome

Epidemiology

Prevalence: 1:2,000 to 5,000 liveborn females

Risk Factors

Genetics

  • Genotype frequencies
    • 45,X 55%
    • 46,Xi(Xq) 17%
    • 45,X/46,XX 13%
    • 46,Xr(X) 5%
    • 45,X/46,XY 5%
    • Other 5%
  • Recurrence risk is low in subsequent pregnancies in the absence of familial X chromosome defects.

Pathophysiology

  • Deletion of the SHOX gene at Xp22.33 is responsible for the majority of the height deficit in affected patients.
  • Fetuses with Turner syndrome have accelerated loss of germ cells from the second half of gestation through the first few years of life, with eventual gonadal failure.

Commonly Associated Conditions

  • Short stature (~100%)
  • Hypogonadism (90%)
  • Sensorineural hearing loss in adults (60%)
  • Hypertension (50%)
  • Glucose intolerance in adults (40–50%)
  • Autoimmune thyroiditis (27%)
  • ADHD (24%)
  • Conductive hearing loss (21%)
  • Renal collecting system abnormalities (20%)
  • Strabismus/hyperopia (17%)
  • Bicuspid aortic valve (16%)
  • Coarctation of the aorta (11%)
  • Horseshoe kidney (10%)
  • Celiac disease (6%)
  • Aortic dissection (1–2%)

-- To view the remaining sections of this topic, please or --

Basics

Description

Presence of typical findings in a phenotypic female with complete or partial absence of the second sex chromosome

Epidemiology

Prevalence: 1:2,000 to 5,000 liveborn females

Risk Factors

Genetics

  • Genotype frequencies
    • 45,X 55%
    • 46,Xi(Xq) 17%
    • 45,X/46,XX 13%
    • 46,Xr(X) 5%
    • 45,X/46,XY 5%
    • Other 5%
  • Recurrence risk is low in subsequent pregnancies in the absence of familial X chromosome defects.

Pathophysiology

  • Deletion of the SHOX gene at Xp22.33 is responsible for the majority of the height deficit in affected patients.
  • Fetuses with Turner syndrome have accelerated loss of germ cells from the second half of gestation through the first few years of life, with eventual gonadal failure.

Commonly Associated Conditions

  • Short stature (~100%)
  • Hypogonadism (90%)
  • Sensorineural hearing loss in adults (60%)
  • Hypertension (50%)
  • Glucose intolerance in adults (40–50%)
  • Autoimmune thyroiditis (27%)
  • ADHD (24%)
  • Conductive hearing loss (21%)
  • Renal collecting system abnormalities (20%)
  • Strabismus/hyperopia (17%)
  • Bicuspid aortic valve (16%)
  • Coarctation of the aorta (11%)
  • Horseshoe kidney (10%)
  • Celiac disease (6%)
  • Aortic dissection (1–2%)

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