Turner syndrome is a chromosomal condition that influences development in individuals assigned female at birth, affecting approximately 1 in 2,000 to 2,500 live female births. The condition arises from a difference in the sex chromosomes, impacting a wide range of developmental processes. The effects of the condition can vary significantly from person to person.
Genetic Origins of Turner Syndrome
Every human cell typically contains 46 chromosomes, including two sex chromosomes that determine biological sex. Females usually have two X chromosomes, while males have one X and one Y. Turner syndrome occurs when one of the X chromosomes is completely or partially missing in a female’s cells. This genetic alteration is not typically inherited from a parent; instead, it is the result of a random error during the formation of reproductive cells.
The most common form is Monosomy X, where every cell in the body has only one X chromosome. Another primary type is mosaic Turner syndrome, where some cells have the typical two X chromosomes while other cells are missing one. The presence of Y chromosome material in a small percentage of cases can also occur, which influences biological development.
Associated Physical and Developmental Traits
The physical characteristics of Turner syndrome can be diverse. One of the most consistent traits is short stature, which often becomes apparent by around age five. Other common external features include:
- A low hairline at the back of the neck
- Low-set ears
- A broad chest with widely spaced nipples
- A webbed neck, characterized by extra folds of skin
- Swelling of the hands and feet (lymphedema), especially at birth
Beyond external appearance, Turner syndrome is associated with internal health considerations. Common issues include congenital heart defects, kidney and urinary tract abnormalities, progressive hearing loss, and vision problems.
The condition also impacts the ovaries. In most cases, the ovaries do not develop properly, leading to a condition known as gonadal dysgenesis. This results in reduced production of sex hormones and infertility. The lack of hormone production also means that most individuals do not undergo puberty without medical intervention.
Diagnosis and Screening
Turner syndrome can be identified at different life stages, from before birth to adulthood. Prenatal diagnosis may be prompted by findings on a routine ultrasound, such as heart or kidney abnormalities. If these signs are present, screening tests like non-invasive prenatal testing (NIPT), which analyzes fetal DNA from the mother’s blood, can be performed. For a definitive prenatal diagnosis, procedures like chorionic villus sampling (CVS) or amniocentesis are used to collect fetal cells for genetic analysis.
After birth, the diagnosis is confirmed through a blood test called a karyotype. This test creates a visual map of an individual’s chromosomes, allowing medical professionals to see their number and structure. The karyotype will show that some or all cells are missing an X chromosome or have a structurally altered one, confirming a total of 45 chromosomes instead of 46. Diagnosis may occur in infancy if characteristic physical features are noticed, or later if a girl experiences slow growth or does not enter puberty as expected.
Managing Health and Development
Management of Turner syndrome focuses on proactive, lifelong medical care to address its health aspects. There is no cure, but therapies can effectively manage the symptoms. Two principal treatments are growth hormone therapy and estrogen replacement therapy. Human growth hormone, administered through injections, can increase final adult height, especially when started in early childhood. The average adult height for untreated women is around 4 feet 8 inches, but this can be increased with treatment.
Estrogen replacement therapy is typically initiated around the age of 11 or 12 to induce the changes of puberty, such as breast development. This therapy also maintains bone density and supports cardiovascular health throughout life. It usually continues until the average age of menopause.
Because the condition can affect multiple body systems, a multidisciplinary healthcare team is needed. This team may include specialists such as cardiologists for heart health, endocrinologists for hormone therapies, and nephrologists for kidney issues. Regular screenings for associated conditions like high blood pressure, thyroid problems, and hearing loss are a standard part of care. With consistent medical oversight and treatment, individuals with Turner syndrome can lead healthy, independent lives.