What is Turner’s Syndrome?
Turner’s Syndrome or gonadal dysgenesis is a condition that affects females in which one of the sex chromosomes (X chromosome) is completely missing or has abnormalities. A normal female has 46 chromosomes, including 2 X-chromosomes (44XX). With Turner’s syndrome, the female patient only has one X chromosome or has an abnormality in one of the X-chromosome. Some conditions only have a missing X chromosome in some cells, but not others. This condition is called Turner’s mosaicism.
Turner’s syndrome occurs in 0.05% of the female population. It is a genetic disorder that usually affects the sexual development of females. Several physical abnormalities are noted with a distinct short stature, webbed neck and low-set ears. Since the X chromosome is affected, there is a gonadal dysfunction or the ovaries do not work, leading to infertility and absence of menses (amenorrhea). Aside from sexual dysfunction, individuals with Turner’s syndrome have cognitive limitations specifically in memory, mathematical and spatial skills.
Since the gonads develop in the same germ layer as other organs, Turner’s syndrome is often accompanied by heart and kidney problems.
History of Turner’s Syndrome
It is named after an endocrinologist who first described it, Henry H. Turner. Turner’s syndrome is commonly called Bonnevie-Ullrich-Turner syndrome or Ullrich-Turner syndrome in Europe because early doctors there also described the disease. The first case of Turner’s syndrome was a 45X karyotype in a 14 year old girl from London.
Causes of Turner’s Syndrome
Predisposing factors for Turner’s syndrome remain unknown. Genetics play a part in the occurrence of the condition. About two-thirds of the cases have inactivated X chromosome, which is paternal in origin. The main cause for Turner’s syndrome is still being studied, but some theories support its development. One theory is that during conception a part of the sex chromosomes is not passed on to the female fetus. These females do not have Barr bodies (part of the X chromosome) which leads to the absence of one X chromosome or incomplete X chromosome.
Turner’s Syndrome Symptoms
The defect in the sex chromosome often leads to the following manifestations:
- Webbed neck
- Short stature
- Broad chest
- Shield shaped chest
- Lymphedema or swelling of the feet and hands
- Wide-spaced nipples
- Low-set ears
- Low hairline
- Sparse pubic hair
- Rudimentary gonads (ovaries) which eventually become fibrosed
- Dryness of the vagina
- Amenorrhea or absence of menses
- Short metacarpals
- Small, soft fingernails
- Micrognathia or small lower jaw
- Narrow maxilla
- Turned-in elbows
- Dry eyes
- Drooping eyelids
- Pigmented moles
- Poor breast development
- Coarctation of the aorta
- Structural defects of the aortic valve
- Misshapen kidneys (horse-shoe)
- Smaller hips or have the same size as the waist (poor hip-to-waist- ratio)
- Poor concentration and memory
- Poor attention
- Learning disabilities
- Dyscalculia or difficulty in math
- Poor spatial skills
- Poor social skills
The occurrence of symptoms is usually different for each female patient. Until now, no two females with Turner’s syndrome have shared the same set of symptoms.
Turner’s Syndrome Diagnosis
Turner’s syndrome can be diagnosed at all stages of life even during fetal development. Turner’s syndrome is usually diagnosed before birth through amniocentesis. Chromosome analysis is done with the specimen. The condition may also be seen during ultrasounds where an abnormality in the kidneys and heart is detected. When Turner’s Syndrome is detected before delivery, parents undergo genetic counseling to help them cope with the condition.
To determine the exact genetic problem in an individual female, karyotyping is done. Karyotyping is the analysis of the chromosomes and chromosomal compositions of an individual. A blood examination is also carried out to determine levels of follicle stimulating hormone and luteinizing hormone. These hormones are usually affected by the change in estrogen levels.
The physician also does a physical examination to determine any underdevelopment or abnormality in the body parts such as the breasts, hands, fingers and feet.
Other diagnostic tests are also done to determine any complications and underlying conditions of the heart, chest, kidneys and reproductive organs. Echocardiogram, MRI, pelvic exam and ultrasound of the ovaries and kidneys are done to determine these conditions.
Treatment of Turner’s Syndrome
The genetic abnormality in Turner’s Syndrome has no cure. However, certain supportive treatments can be done to correct the symptoms. These include:
Growth Hormone Therapy
Growth hormone enhances bone growth to let girls with Turner’s Syndrome reach an average height and treatment may start as early as in the toddler years. It is approved by the Food and Drug Administration for the management of Turner’s Syndrome. When this is not given, females only reach an average height of less than five feet.
Estrogen Replacement Therapy
Sex hormones are usually given to improve sexual development. Estrogen therapy is usually administered starting at 12 years old. It improves breast development, pubic hair growth; and increases the width of the pelvis and the development of other secondary sex characteristics. Estrogen is also essential for bone and tissue health. Individuals with Turner’s Syndrome who do not receive estrogen therapy are likely to develop osteoporosis. Estrogen is also important for uterine maturity when a woman wants to bear a child.
Assisted Reproduction Techniques
Physicians also assist the woman with certain reproduction techniques to help her become pregnant such as the use of donor eggs. These turn into embryos which are then carried by the woman with Turner’s syndrome.
The treatment for Turner’s Syndrome relies on improving the growth and sexual functioning of the woman. Since the condition is associated with chromosomal aberrations, there is no current cure to completely eradicate the condition.
Turner’s syndrome is a lifelong condition. The patient can usually have a normal life if treatments are carefully monitored. Symptoms of the condition are not harmful for the patient, but certain underlying conditions may contribute to mortality in some cases.
Females with Turner’s Syndrome usually reach 50 years of age. The reduction in life expectancy is up to 13 years. However, when complications are not detected, patients often die at an early age due to kidney and heart problems. A fetus having the condition in the uterus often ends up as still born or spontaneously aborted during the early stage of conception because of the congenital anomalies.
Humans have a total of 46 chromosomes including two sex chromosomes. These chromosomes contain the genes and DNA responsible for building the body. The sex chromosomes indicate the sex of the person. Females have two X chromosomes (XX) while males have one X and one Y chromosome (XY).
In Turner’s Syndrome, there is a defect in one of the X chromosome of the female; either it is absent or has defects. The most common karyotype of individuals with Turner’s Syndrome is 45XO or a non disjunction of the chromosomes. In these cases, there are 44 chromosomes with only one sex chromosome (44 plus one is 45 – written as 45XO, the O signifies the absent X chromosome.)
During conception, the sex chromosomes are not transferred properly leading to the condition. Genetic counseling should be done with parents with an offspring with Turner’s Syndrome, although recurrences with following pregnancies are usually low.
Complications of Turner’s syndrome are commonly associated with the organs that develop in the same germ layer as the reproductive organs such as:
1. Heart defects – Cardiovascular complications or congenital heart defects are the number one reason for mortality in patients with Turner’s Syndrome. Reduced life expectancy is associated with these complications. Up to 45% of patients with Turner’s Syndrome have congenital heart problems.
Obstructive lesions in the left side of the heart are commonly seen which significantly reduce the blood flow in the heart. The most common congenital heart anomalies include post-ductal coarctation of the aorta, bicuspid aortic valve, partial anomalous venous drainage, aortic valve stenosis, aortic dissection, dilatation and rupture and hypoplastic left heart syndrome.
2. Diabetes – Diabetes is a potential result of obesity in Turner’s syndrome. Type 1 diabetes can also occur during childhood as a result of affectation of the cells in the pancreas that produce insulin. Diabetes can be prevented through weight reduction.
3. Kidney problems – Kidney abnormalities include abnormal kidney tubules, a horse-shoe kidney, or a poor renal blood flow. About 30% of women with Turner’s Syndrome have kidney abnormalities. Kidney problems are often corrected through surgery although the kidney problem does not often result in serious conditions.
4. Scoliosis and Bone Fractures – The normal skeletal development is affected due to inadequate synthesis of estrogen. This results in osteoporosis and eventually scoliosis because of the exacerbation of the curvature of the spine. Bone fractures may also develop as a result of osteoporosis.
5. Thyroid problems – Individuals with Turner’s Syndrome may also develop hypothyroidism such as Hashimoto’s thyroiditis.
6. Infertility – This results from the underdevelopment and fibrosis of the ovaries bilaterally. It is often corrected by supportive treatments such as egg donation from normal women.
7. Cognitive Problems – Individuals do not experience mental retardation, but only learning disabilities or non-verbal learning disorders. These include poor spatial skills, memory and math skills. These difficulties often lead to problems in everyday functions although most adults with Turner’s Syndrome may lead productive lives.
A special type of Turner’s syndrome, which is Ring-X Turner’s Syndrome, may lead to mental retardation. This type accounts for up to 4% of all cases of Turner’s Syndrome.
Other complications include obesity, high blood pressure, cataracts and arthritis.
There is no known way to prevent Turner’s Syndrome because the exact cause and risk factors are still unknown.
23rd chromosome missing in Turners syndrome
Picture 2 – Symptoms and signs of Turners syndrome
Image source – mun.ca
Picture 3 – broad shield chest in Turner’s syndrome
Image source – wikia.com
Picture 4 – Puffy Feet in Turners syndrome
Image Source – wikimedia.org
Turner’s syndrome baby Photo
Image Source – Turnersyndromepictures.com
Updated by Andrea at 11.50pm on 23/8/15.