Turner’s Syndrome

Overview – Turner’s Syndrome

Turner’s syndrome is a chromosomal disorder that affects biological females who are missing all or part of one X chromosome. Also known as 45,X or monosomy X, it is one of the most common sex chromosome abnormalities, though most cases result in miscarriage. Survivors often exhibit a distinct pattern of physical features, developmental issues, and infertility, with diagnosis often occurring at various stages of life depending on presentation.

Definition

Turner’s syndrome (45,X) is a chromosomal condition affecting females, caused by complete or partial absence of one X chromosome. It may present as a full monosomy, mosaicism, or structural abnormalities of the X chromosome.

Aetiology

• Chromosomal cause:
  • Total or partial loss of one X chromosome
  • Can be:
    • Monosomy X (45,X): Classic and most severe form
    • Mosaicism: Some cells have 45,X, others have 46,XX or structural variants
• Origin:
  • Random error in paternal gametogenesis or early embryonic cell division
  • Not typically inherited

Clinical Features

Prenatal and Neonatal:

• Many affected pregnancies result in miscarriage
• Cystic hygroma, hydrops fetalis, or congenital heart defects may be seen on antenatal scan

Postnatal and Childhood:

• Short stature (often presenting in late childhood)
• Webbed neck
• Low posterior hairline
• Broad chest with widely spaced nipples
• Lymphoedema of hands and feet (especially at birth)
• Delayed puberty or absent secondary sexual characteristics
• Infertility (due to ovarian dysgenesis)

Cardiovascular and Endocrine:

• Coarctation of the aorta
• Bicuspid aortic valve
• Hypertension
• Increased risk of type 2 diabetes and autoimmune thyroid disease (e.g. Hashimoto’s)

Other:

• Mild learning difficulties (particularly in spatial reasoning or mathematics)
• Hearing loss (conductive or sensorineural)
• Normal intelligence in most, but specific cognitive profiles vary

Investigations

• Prenatal diagnosis:
  • Chorionic villus sampling or amniocentesis may identify 45,X
• Postnatal diagnosis:
  • Based on clinical signs or growth/puberty concerns
  • Confirmed with karyotype analysis
• Further assessments may include:
  • Echocardiography
  • Renal ultrasound
  • Hearing assessments
  • Endocrine panel (thyroid, glucose)

Management

• Growth hormone therapy:
  • Started in childhood to improve adult height
• Oestrogen replacement therapy:
  • Initiated around the age of expected puberty to induce secondary sexual development
  • Later followed by cyclical progesterone
• Fertility counselling:
  • Most are infertile; egg donation and assisted reproduction may be options
• Cardiac surveillance:
  • Regular follow-up for congenital heart defects and hypertension
• Audiology and ENT care
• Multidisciplinary support:
  • Including endocrinology, cardiology, ENT, psychology, and reproductive medicine

Complications

• Infertility
• Congenital heart disease (especially coarctation of the aorta)
• Hearing loss
• Increased risk of metabolic syndrome
• Osteoporosis (if hypogonadism is untreated)

Differential Diagnosis

• Noonan syndrome (shares some physical features but occurs in both sexes)
• Constitutional delay of growth and puberty
• Other causes of primary amenorrhoea

Summary – Turner’s Syndrome

Turner’s syndrome (45,X) is a chromosomal disorder in females, caused by partial or complete loss of one X chromosome. It presents with short stature, infertility, distinctive physical traits, and a range of associated complications, including cardiovascular and endocrine issues. Early diagnosis and multidisciplinary care can greatly improve quality of life. For more, visit our Genetics & Cancer Overview page.