Turner syndrome
Chromosomal disorder in females with one X chromosome.
Turner syndrome (TS), commonly known as 45,X or 45,X0, is a chromosomal disorder in which cells of females have only one X chromosome instead of two, or are partially missing an X chromosome. It is a sex chromosome monosomy leading to the complete or partial deletion of pseudoautosomal regions. The condition was first described by American endocrinologist Henry Turner in 1938, and in 1964 it was determined to be due to a chromosomal abnormality. Turner syndrome occurs in between one in 2,000 and one in 5,000 females at birth, affecting all regions and cultures about equally.
Quick Facts
- Field
- Pediatrics, medical genetics
- Symptoms
- Neck webbing, short stature, heart defects, ptosis, cupped ears
- Onset
- At birth
- Onset Always
- y
- Duration
- Lifetime
- Causes
- 1 X chromosome and no Y chromosome
- Risks
- Nondisjunction in eggs
- Diagnosis
- Karyotype
- Frequency
- 1 in 2,000 to 5,000 female births
- Named After
- Henry Turner
Facts from the source article.
Lore & Background
Turner syndrome is caused by one X chromosome (45,X), a ring X chromosome, 45,X/46,XX mosaicism, or a small piece of the Y chromosome in what should be an X chromosome. The chromosomal abnormality often occurs during formation of reproductive cells in a parent or in early cell division during development. No environmental risks are known, and the mother's age does not play a role. Most people have 46 chromosomes, but those with Turner syndrome usually have 45 in some or all cells. In cases of mosaicism, symptoms are usually fewer, and possibly none occur at all. Diagnosis is based on physical signs and genetic testing.
Signs and symptoms vary but often include a short webbed or wide neck, arched palate, low-set ears, low hairline at the nape of the neck, short stature, and lymphedema of the hands and feet. Those affected do not normally develop menstrual periods or mammary glands without hormone treatment and are unable to reproduce without assistive reproductive technology. Heart defects, Type 2 diabetes, and hypothyroidism occur more frequently than average. Most people with Turner syndrome have normal intelligence; however, some have problems with spatial visualization that can hinder learning mathematics. Ptosis and conductive hearing loss also occur more often than average.
Reader's Guide
Turner syndrome is significant as a common chromosomal disorder that provides insight into sex chromosome biology and the role of the SHOX gene in growth. The condition's association with short stature, heart defects, and infertility has shaped clinical management protocols, including growth hormone therapy and estrogen replacement. The discovery that mosaicism can produce milder phenotypes or even male presentation in 45,X0/46,XY cases highlights the complexity of chromosomal variation. The syndrome's legacy includes advancing understanding of pseudoautosomal regions and the genetic basis of stature. No cure exists, but treatments such as human growth hormone injections during childhood can increase adult height, and estrogen replacement therapy promotes breast and hip development. Generally, people with Turner syndrome have a shorter life expectancy, mostly due to heart problems and diabetes. The condition affects all regions and cultures about equally, and incidental diagnosis through biobank samples or prenatal testing finds many girls and women with few traditional signs.
Did You Know?
- Around 40%–50% of cases are true monosomy X with a 45,X0 karyotype.
- The mean adult height of women with Turner syndrome without growth hormone therapy is about 20 cm shorter than the general female mean.
More in Growth disorders 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced