Turner syndrome is a chromosomal disorder that affects only females. It involves a lack of part or all of a second sex chromosome in some or all cells.
Girls are often short in stature, and they may have some emotional and learning difficulties, but most will have normal intelligence.
Turner syndrome (TS) is also known as Turner’s syndrome, 45,X syndrome, Ullrich-Turner syndrome, or Gonadal dysgenesis.
What is Turner syndrome?
Turner syndrome is a chromosomal disorder.
People without Turner syndrome have 46 chromosomes, of which two are sex chromosomes. Females have two X chromosomes.
However, individuals with Turner syndrome do not have part of a second sex chromosome. Sometimes the whole chromosome will be absent.
Around 1 in 2,500 girls is born with the condition, but it probably affects more pregnancies that do not survive to term. In the United States, around 70,000 women are thought to have TS.
Life expectancy is slightly lower than it would be for most people.
Chromosomes are strands of deoxyribonucleic acid (DNA) that exist in all the cells of the human body. Chromosomes contain instructions that make a human’s behavioral and physical characteristics.
There are two types of Turner syndrome:
In classical Turner syndrome, an X chromosome is completely missing. This affects about half of all people with TS.
Mosaic Turner syndrome, mosaicism, or Turner mosaicism is where the abnormalities occur only in the X chromosome of some of the body’s cells.
The signs and symptoms of Turner syndrome vary considerably. They may even appear before birth.
Signs and symptoms before birth include lymphedema. Lymphedema happens when fluid is not properly transported around the organs of the fetal body, and excess fluid leaks into the surrounding tissue, resulting in swelling.
Newborns with TS may have swollen hands and feet.
The fetus may have:
thick neck tissue
cystic hygroma, or swelling of the neck
lower than normal weight
At birth or during infancy, there may be:
a broad chest with widely-spaced nipples
cubitus valgus, where arms turn outwards at the elbows
fingernails that turn upward
a high, narrow palate, or roof of the mouth
low hairline at the back of the head
small and receding lower jaw
slower or delayed growth
smaller height and weight at birth
swelling of the hands and feet
wide neck with extra folds of skin, sometimes described as “web-like”
In some cases, TS may not become apparent until later on.
Later signs and symptoms include:
Irregular growth: Growth spurts may not occur at expected childhood times. During the first 3 years of life, the infant may have normal height, but by the age of 3 years, their growth rate will be lower than average, and by the age of 5 years, short stature will be noticeable.
Short stature: An adult female may be about 8 inches, or 20 centimeters, shorter than expected for an adult female member of that family, unless they have treatment.
Most girls with TS have normal intelligence and good verbal and reading skills, but some may have problems with math, spatial concepts, memory skills, and fine finger movements.
Social problems include difficulty interpreting other people’s reactions or emotions.
Normally, during puberty, a female’s ovaries start producing the sex hormones, estrogen, and progesterone. Most girls with TS will not produce these sex hormones.
This leads to:
no onset of menstrual periods
poorly developed breasts
Although a female with TS has non-functioning ovaries and is infertile, her vagina and uterus, or womb, is usually normal, and most females with TS will be able to have a normal sex life.
Around 20 percent of females with TS will start menstruating during puberty, but it is rare for a woman with TS to become pregnant without fertility treatment.
Other possible signs and symptoms include:
eyes that slant downwards
mouth abnormalities that can cause dental problems
narrowing of the aorta, which may result in a heart murmur
hypothyroidism, or an underactive thyroid gland, treatable with thyroxine tablets
hypertension or high blood pressure
osteoporosis, or brittle bones, due to insufficient estrogen
otitis media, middle ear infection, or glue ear, is common among young girls with TS
hearing loss in adulthood may be due to otitis media during childhood
diabetes is more likely in older and overweight females with TS than in other women with similar weight and age
moles may be prevalent on the skin
small spoon-shaped nails
a fourth finger or toe that is shorter than normal
Causes and risk factors
Most people are born with two sex chromosomes. Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.
When a female has TS, one X chromosome copy is either absent or significantly altered.
A number of genetic alterations are possible in TS.
Monosomy: One X chromosome is completely missing. Experts believe this is caused by an error either in the father’s sperm or the mother’s egg. Every cell in the offspring’s body has one X chromosome missing.
Mosaic Turner syndrome, also called mosaicism or Turner mosaicism: During the early stages of fetal development, an error may occur in cell division, resulting in some cells having two X chromosome copies, while others only have one. Sometimes, there may be some cells with both X chromosome copies, and others with one altered copy.
Y chromosome material: A small number of people with TS have some cells with just one X chromosome copy, and others with just one X chromosome copy and some Y chromosome material. The individual develops as a female but with a higher risk of developing a type of cancer known as gonadoblastoma.