Turner Syndrome

In Turner Syndrome, a female typically has 45 chromosomes instead of the normal 46. This is due to the fact that the female may be missing either partially or completely an X chromosome, which is related to the genetic condition.

Table of Contents:

[Turner Syndrome - Overview](#Turner Syndrome - Overview)

[Turner Syndrome Causes and Types](#Turner Syndrome Causes and Types)

[Turner Syndrome Symptoms](#Turner Syndrome Symptoms)

Turner Syndrome Diagnosis

[Turner Syndrome Treatment](#Turner Syndrome Treatment)

[Frequently Asked Questions](#Frequently Asked Questions)

Turner Syndrome - Overview

Turner Syndrome, also known as monosomy of the X chromosome, is a genetic disorder that is caused by the partial or complete loss of one of the X chromosomes in females. This disorder can lead to various developmental problems and put those affected at risk of many diseases.

Henry H. Turner described the condition first in 1938, thus resulting in the name Turner Syndrome.

Turner syndrome is the only chromosomal anomaly that is viable when only one copy of a chromosome is present.

Effects of Turner Syndrome

Turner Syndrome is a genetic disorder which causes retarded sexual development in females, and is associated with other physical and mental difficulties. These include sterility, short stature, webbing of the skin in the neck region, cardiac abnormalities, hearing impairment, and vision loss. Unfortunately, there is no cure for this disorder, but treatment can help to mitigate the effects of learning difficulties, short stature, and sexual development. Diagnosis of Turner Syndrome can be made through antenatal tests during pregnancy, or through a karyotype test.

Karyotype of Turner Syndrome (Monosomy of X Chromosome)

Turner Syndrome: Causes and Types

Turner Syndrome is a genetic disorder caused by aneuploidy of the sex chromosome, resulting in either one X chromosome missing in all cells or some cells. This condition is only seen in females.

The occurrence of Turner syndrome is 1 in every 2,500 female births.

The causes of Turner Syndrome can be varied.

1. Monosomy of X (XO): This accounts for half of the Turner syndrome cases, in which there is a complete loss of one X chromosome. This results from an abnormal cell division during gamete formation, causing eggs or sperm to lack a sex chromosome. People with this type of Turner syndrome have all their cells lacking one X chromosome, i.e. they have 45 chromosomes in all the cells. Additionally, people with XO are found to have no Barr bodies, meaning the X chromosome present is not inactivated. However, active genes are required in pairs for proper growth and development.

2. Mosaicism: When the sex chromosome is lost during mitosis after fertilisation, resulting in some cells with 45 chromosomes (one X chromosome) and some cells having normal 46 chromosomes (XX chromosomes), it is known as mosaicism. When the loss occurs early in the development, there are a large number of cells with 45 chromosomes and they develop the symptoms of Turner syndrome. If the loss occurs late in the development, the number of aneuploid cells are less, thus reducing the severity of the symptom. In some cases of somatic mosaics, there is a presence of 45 X cells and some cells with an extra X chromosome, i.e. 47 XXX. Girls with this type of genetic constituent tend to be taller.

In some females with Turner Syndrome, there can be a small number of cells with a Y chromosome, i.e. 46 XY, in addition to the 45 X cells. This puts them at a higher risk of developing a type of cancer known as Gonadoblastoma.

1. X Chromosome Abnormalities: In approximately 20% of cases of Turner Syndrome, two X chromosomes are present in the cells, however, one X chromosome has an abnormal structure. This can be due to the presence of a circular shaped chromosome with joined ends, known as a ring chromosome. Additionally, an isochromosome can be present, which is an X chromosome with two long arms instead of one short and one long arm. Lastly, some of the genetic material can be missing due to a deletion of one X chromosome.

Turner Syndrome Symptoms

Individuals with Turner Syndrome may experience a variety of symptoms, depending on their genetic makeup. Most commonly, individuals with Turner Syndrome are female, have rudimentary ovaries which makes them sterile, and have a short stature.

Main symptoms of Turner syndrome include:

• Short stature
• Webbed neck
• Low hairline
• Broad chest
• Drooping eyelids
• High-arched palate
• Low-set ears
• Abnormal fingernails or toenails

Common facial features such as drooping eyelids, a narrow palate, small jaws, and low-set, prominent earlobes

Growth is irregular, with no regular growth spurts and delayed puberty.

Short stature relative to other females

Females may have normal intelligence and good reading and verbal skills, but they may also experience certain learning difficulties, such as difficulty with memorization, difficulty with mathematics, and difficulty with spatial concepts.

They could have difficulty with non-verbal communication and interpreting the emotions of others.

Poorly developed breasts, delayed or absent onset of the menstrual cycle, and infertility

The murmuring of the heart can be caused by a narrowing of the aorta, as well as other abnormalities that are related to the heart, liver, and kidney.

Hypothyroidism and hypertension are frequent

Osteoporosis is caused by insufficient estrogen.

Chronic middle ear infection leading to hearing loss

Symptoms of Turner syndrome can be observed in the developing fetus as well.

Lymphedema is characterized by swelling caused by an accumulation of fluid in the body.

Swelling or Thickness of the Neck

Lower than normal weight

Turner Syndrome Diagnosis

Turner Syndrome can be diagnosed during pregnancy through an ultrasound or by specific tests such as amniocentesis to determine the karyotype of the fetus.

At birth, Turner syndrome can be identified by signs such as swelling in hands and feet, heart or kidney issues, webbed neck, and a broad chest with widely spaced nipples.

Sometimes Turner syndrome is not diagnosed until the adolescent stage, when puberty does not occur.

Turner Syndrome Treatment

There is no cure for Turner Syndrome; however, treatments may be available to address complications related to the condition, such as sexual development, hearing and vision impairment, and infertility.

Preventive care can help to maintain good health by monitoring conditions such as heart complications and thyroid.

Hormone therapy can be beneficial for those with short stature, as it can help induce sexual development and reduce associated risks.

IVF can be beneficial for a female with Turner Syndrome who wishes to become pregnant.

Learning difficulties can be overcome with proper training and educational support.

Additional Resources:

Short Notes Of Biology For NEET: Aneuploidy

Chromosomal Disorders in Humans

What Causes Down Syndrome?

Molecular Basis of Inheritance: Learn with Flashcards

Principles Of Inheritance And Variation

Frequently Asked Questions

The chromosome number in Turner Syndrome is 45,X.

Doctors use a karyotype test for the diagnosis of Turner syndrome, which is related to the X chromosome. The outcome of this test indicates Turner syndrome when it displays only one X chromosome instead of the normal two X chromosomes, resulting in a total chromosome number of 45 instead of 46.

Yes, Turner Syndrome is an XXY condition.

Turner syndrome is caused when a female is either partially or completely missing an X chromosome. This is due to the X chromosome related nature of the condition.

Turner syndrome is caused by aneuploidy of the sex chromosome in females, resulting in either one X chromosome missing in all the cells, or some cells having one X chromosome missing. It is also referred to as the 45,X condition.

Symptoms of Turner Syndrome include:

• Short stature
• Webbed neck
• Low hairline at the back of the neck
• Swelling (lymphedema) of the hands and feet
• Heart defects
• Kidney problems
• Hearing loss
• Diabetes
• Vision problems

Usually, individuals with the condition experience varying signs and symptoms, such as short and webbed necks, short stature, low-set prominent earlobes, and swollen feet and hands (especially in females).