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Turner syndrome
Also known as 45,X · Monosomy X · 45,X0
Turner syndrome typically affects individuals assigned female at birth, leading to a range of developmental and medical concerns. It can impact growth, heart development, and fertility, requiring lifelong medical care.
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Overview
Turner syndrome, also known as 45,X or Monosomy X, is a chromosomal condition that occurs when an individual assigned female at birth has only one X chromosome, or part of one X chromosome is missing [PMID:33678077]. Instead of the usual two X chromosomes (XX), individuals with Turner syndrome have a 45,X karyotype or a variation of it. This condition is not typically inherited and usually happens randomly during the formation of reproductive cells or early foetal development.
Turner syndrome can lead to a variety of features, which vary significantly among affected individuals. These may include short stature, distinct facial characteristics, and heart abnormalities. The condition can also impact kidney function, thyroid function, and bone health, and typically results in infertility.
Symptoms & clinical features
The clinical features of Turner syndrome can be diverse and may be apparent at different stages of life. In newborns and infants, common signs may include swelling (lymphoedema) in the hands and feet, a wide or webbed neck, and a low hairline. Many individuals with Turner syndrome experience short stature, which can become noticeable during childhood and persist into adulthood [PMID:34479379].
During adolescence, affected individuals often experience delayed or absent puberty, due to ovarian dysfunction. Other common features may include a broad chest with widely spaced nipples, downward-slanting eyes, and a small lower jaw. Some individuals may also have a higher arch in the roof of their mouth or frequent ear infections. The range and severity of these features can differ greatly from person to person.
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Affected organs
Turner syndrome can affect several organ systems. The heart is frequently involved, with congenital heart defects, such as a bicuspid aortic valve (an aortic valve with two flaps instead of the usual three) or coarctation of the aorta (a narrowing of the main artery that carries blood from the heart), being common [PMID:33678077]. Kidney abnormalities, such as horseshoe kidneys or duplication of the renal collecting system, can also occur.
Endocrine organs are often affected, leading to conditions like an underactive thyroid (hypothyroidism) or type 2 diabetes. The reproductive organs, particularly the ovaries, are typically underdeveloped, resulting in premature ovarian insufficiency and infertility. Bone health can also be impacted, with an increased risk of osteoporosis.
Risks & severity
The severity of Turner syndrome varies widely; some individuals have mild features, while others experience more significant health challenges. Short stature is a consistent feature, often requiring growth hormone treatment. The risk of heart problems, including high blood pressure, increases with age. There is also an elevated risk of developing autoimmune conditions, such as autoimmune thyroiditis [PMID:34479379].
Individuals with Turner syndrome are at an increased risk for hearing loss, ear infections, and some kidney problems. Learning difficulties, particularly with spatial reasoning and maths, can occur, though intellectual disability is not typically a feature. Due to ovarian dysfunction, most individuals with Turner syndrome are infertile, although assisted reproductive technologies can sometimes be an option.
Genetic causes
Turner syndrome is caused by a chromosomal abnormality where an individual has only one functional X chromosome, instead of the usual two. This can be a complete absence of one X chromosome (45,X), or it can involve the partial absence or structural alteration of one X chromosome. In some cases, mosaicism occurs, where some cells have the 45,X karyotype while other cells have a typical 46,XX karyotype or another variation.
The SHOX gene, located on the X chromosome and also found on the Y chromosome, plays a critical role in skeletal development, particularly for long bone growth. Loss of a functional copy of the SHOX gene, which is often seen in individuals with Turner syndrome, is thought to contribute significantly to the characteristic short stature observed in the condition.
- SHOX SHOX homeobox
Inheritance pattern
Turner syndrome is generally not inherited in families. It typically occurs as a random event during the formation of egg or sperm cells, or during early foetal development. This means that a parent's genetics usually do not cause their child to develop Turner syndrome, and it is uncommon for more than one child in a family to have the condition.
In rare instances, if a parent has mosaic Turner syndrome (meaning some of their cells have the 45,X karyotype), there might be a very small chance of passing on the chromosomal change. However, for most families, the occurrence of Turner syndrome is considered sporadic.
Diagnosis & testing
The diagnosis of Turner syndrome is typically confirmed through a genetic test called a karyotype, which analyses the number and structure of an individual's chromosomes. This test can identify the characteristic 45,X chromosomal pattern or its variations. Diagnosis can sometimes occur before birth through prenatal testing, such as amniocentesis or chorionic villus sampling, or it may be suspected based on ultrasound findings.
After birth, diagnosis can be made at any age, often when a child presents with features like short stature, delayed puberty, or specific congenital heart defects. Clinical geneticists or paediatricians often refer individuals for genetic testing. In the UK, genetic testing for suspected chromosomal conditions such as Turner syndrome would fall under the NHS Genomic Medicine Service, aligning with relevant R-codes for rare and inherited diseases.
Management & lifestyle
Management of Turner syndrome focuses on addressing the specific medical and developmental needs of each individual, as recommended by a multidisciplinary team. Growth hormone therapy is often initiated in childhood to help improve adult height. Oestrogen replacement therapy is typically started during adolescence to induce puberty and support bone health.
Regular monitoring for potential complications is essential, including echocardiograms to check for heart defects, kidney ultrasounds, and thyroid function tests. Specialist paediatricians, endocrinologists, cardiologists, and gynaecologists are often involved in ongoing care. Genetic counsellors can provide valuable information and support regarding the condition and its implications for individuals and families.
UK care pathway
In the UK, individuals with suspected Turner syndrome are typically referred to clinical genetics services or specialist paediatric clinics within the NHS. Genetic testing, often a karyotype analysis, confirms the diagnosis, aligning with the NHS Genomic Medicine Service (GMS) pathway for rare and inherited diseases. Genetic counsellors play a crucial role in explaining the genetic basis of the condition and its implications.
Once diagnosed, care is usually coordinated by a specialist team, often involving paediatric endocrinologists, cardiologists, and other specialists, depending on the individual's specific needs. Ongoing management and surveillance are provided through NHS clinics.
Frequently asked questions
Is Turner syndrome hereditary?
Turner syndrome is typically not inherited from parents. It usually occurs randomly during the formation of reproductive cells or early foetal development. Therefore, it is uncommon for more than one person in a family to have the condition.
Can individuals with Turner syndrome have children?
Most individuals with Turner syndrome experience infertility due to underdeveloped ovaries. However, advancements in assisted reproductive technologies, such as egg donation, may offer options for some individuals to have children. It is important to discuss these options with a fertility specialist.
What is the life expectancy for someone with Turner syndrome?
With appropriate medical management and regular monitoring, individuals with Turner syndrome can live full and healthy lives, though there may be a slightly reduced life expectancy primarily due to cardiovascular complications. Regular check-ups and adherence to treatment plans are crucial.
What support is available for families affected by Turner syndrome?
In the UK, support is available through the NHS, including specialist clinics and genetic counselling services. Patient advocacy groups and charities, such as the Turner Syndrome Support Society, also provide valuable resources, information, and a community for affected individuals and their families.
Does Turner syndrome affect intelligence?
Turner syndrome does not typically cause intellectual disability. Most individuals with Turner syndrome have intelligence within the normal range. However, some may experience specific learning difficulties, particularly with non-verbal skills like spatial reasoning or mathematics. Educational support can be beneficial.
References
- Steiner M, Saenger P. Turner Syndrome: An Update. Advances in pediatrics. 2022. PMID: 35985709
- Freel EM, Mason A. Turner Syndrome. Hypertension (Dallas, Tex. : 1979). 2019. PMID: 30571573
- Khan N, Farooqui A, Ishrat R. Turner Syndrome where are we? Orphanet journal of rare diseases. 2024. PMID: 39198906
- Kesler SR. Turner syndrome. Child and adolescent psychiatric clinics of North America. 2007. PMID: 17562588
- Wan KL, Brown EL, Krishnaswamy R. Turner Syndrome. Journal of paediatrics and child health. 2025. PMID: 40642882
- Milbrandt T, Thomas E. Turner syndrome. Pediatrics in review. 2013. PMID: 24000347
- Mikwar M, MacFarlane AJ, Marchetti F. Mechanisms of oocyte aneuploidy associated with advanced maternal age. Mutation research. Reviews in mutation research. 2020. PMID: 32800274
- Sybert VP, McCauley E. Turner's syndrome. The New England journal of medicine. 2004. PMID: 15371580