Turner syndrome (TS), also known as 45,X, or 45,X0, is a genetic condition in which a female is partially or completely missing an

X chromosome The X chromosome is one of the two sex-determining chromosomes ( allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO se ...

. Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck,

short stature Short stature refers to a height of a human which is below typical. Whether a person is considered short depends on the context. Because of the lack of preciseness, there is often disagreement about the degree of shortness that should be called ' ...

, and swollen hands and feet are seen at birth. Typically, those affected do not develop menstrual periods, or

breasts The breast is one of two prominences located on the upper ventral region of a primate's torso. Both females and males develop breasts from the same embryological tissues. In females, it serves as the mammary gland, which produces and s ...

without hormone treatment and are unable to have children without reproductive technology. Heart defects,

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

, and low thyroid hormone occur in the disorder more frequently than average. Most people with Turner syndrome have normal intelligence; however, many have problems with spatial visualization that may be needed in order to learn mathematics. Vision and hearing problems also occur more often than average. Turner syndrome is not usually inherited; rather, it occurs during formation of the reproductive cells in a parent or in early cell division during development. No environmental risks are known, and the

mother's age Advanced maternal age, in a broad sense, is the instance of a woman being of an older age at a stage of reproduction, although there are various definitions of specific age and stage of reproduction.mosaicism. In these cases the symptoms are usually fewer, and possibly none occur at all. Diagnosis is based on physical signs and genetic testing. No cure for Turner syndrome is known. Treatment may help with symptoms. Human growth hormone injections during childhood may increase adult height. Estrogen replacement therapy can promote development of the

and hips. Medical care is often required to manage other health problems with which Turner syndrome is associated. Turner syndrome occurs in between one in 2,000 and one in 5,000 females at birth. All regions of the world and cultures are affected about equally. Generally people with Turner syndrome have a shorter life expectancy, mostly due to heart problems and diabetes. American endocrinologist Henry Turner first described the condition in 1938. In 1964, it was determined to be due to a chromosomal abnormality.

Presentation

Turner syndrome has a number of physical and psychological impacts, including

, heart defects,

neck webbing A webbed neck, or pterygium colli, is a congenital skin fold that runs along the sides of the neck down to the shoulders. There are many variants. Signs and symptoms On babies, webbed neck may look like loose folds of skin on the neck. As the ...

, delayed or absent puberty, and infertility. The

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...

of Turner syndrome is affected by mosaicism, where cell lines with a single sex chromosome are combined with those with multiple. Around 40%–50% of cases of Turner syndrome are true "monosomy X" with a 45,X0 karyotype, while the remainder are mosaic for another cell line, most commonly 46,XX, or have other structural abnormalities of the X chromosome. The classic features of Turner syndrome, while distinctive, may be rarer than previously thought; incidental diagnosis, such as in biobank samples or prenatal testing for older mothers, finds many girls and women with few traditional signs of Turner syndrome.

Physiological

Height

Relationship between chromosome X dosage in 45, X and 47, XXX females for quantitative traits

Turner syndrome is associated with short stature. The mean adult height of women with Turner syndrome without growth hormone therapy is around shorter than the mean of women in the general population. Mosaicism affects height in Turner syndrome; a large population sample drawn from the UK Biobank found women with 45,X0 karyotypes to have an average height of , while those with 45,X0/46,XX karyotypes averaged . The strength of the association between Turner syndrome and short stature is such that idiopathic short stature alone is a major diagnostic indication. Growth delay in Turner syndrome does not begin at birth; most neonates with the condition have a birth weight in the lower end of the normal range. Height begins to lag in toddlerhood, with a delayed growth velocity becoming apparent as early as 18 months. When girls with Turner syndrome begin school, their height is usually still not remarkably unusual; marked short stature becomes obvious in mid-childhood. In undiagnosed preadolescents and adolescents, growth delay may be mistaken for a side effect of delayed puberty and improperly treated. Short stature in Turner syndrome and its counterpoint, tall stature in sex chromosome polysomy conditions such as Klinefelter syndrome, XYY syndrome, and

trisomy X Trisomy X, also known as triple X syndrome and characterized by the karyotype 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 women but it is rarely diag ...

, is caused by the short-stature homeobox gene on the X and Y chromosomes. The absence of a copy of the ''SHOX'' gene in Turner's inhibits skeletal growth, resulting both in overall short stature and in a distinctive pattern of skeletal malformations including

micrognathia Micrognathism is a condition where the jaw is undersized. It is also sometimes called mandibular hypoplasia. It is common in infants, but is usually self-corrected during growth, due to the jaws' increasing in size. It may be a cause of abnorma ...

(small chin), cubitus valgus (abnormal forearm angles), and short fingers. When Turner syndrome is diagnosed in early life, growth hormone therapy can decrease the degree of short stature. The use of growth hormone therapy in Turner's originated from a series of studies in the 1980s finding it to substantially increase the height of treated girls, compared to prior adult height predictions and Turner's growth charts; treatment with human growth hormone appears to increase expected adult height by approximately from an otherwise expected norm of –. In some cases oxandrolone, a steroid with a relatively mild masculinizing effect, may be used alongside growth hormone. The addition of oxandrolone to a Turner's treatment regimen adds around to the final height. Oxandrolone is used particularly often in girls diagnosed later in their growth period, due to the reduced impact of growth hormone alone in this population. However, oxandrolone use runs the risk of delayed breast development, voice deepening, increased body hair, or clitoromegaly. The effects of growth hormone therapy are at their strongest during the first year of treatment and taper off over time.

Physical features

Preoperative webbed neck in Turner syndrome

In addition to short stature, Turner syndrome is associated with a number of characteristic physical features. These include a webbed neck, a low hairline, a small chin and jaw, a

high-arched palate A high-arched palate (also termed high-vaulted palate) is where the palate is unusually high and narrow. It is usually a congenital developmental feature that results from the failure of the palatal shelves to fuse correctly in development, the sa ...

, and a broad chest with wide-spaced nipples. Lymphedema (swelling) of the hands and feet is common at birth and sometimes persistent throughout the lifespan. Some Turner's stigmata, such as cubitus valgus and shortened fingers, are related to ''SHOX'' gene dosage effects. A number of the external manifestations of Turner syndrome are focused on the limbs, hands, and feet. Lymphedema at birth is one of the classic features of the syndrome; though it often resolves during toddlerhood, recurrence in later life is frequent, often without apparent cause. Cases where the retained X chromosome was inherited from the mother more often experience lymphedema than those where it was from the father. As a consequence of lymphedema's effects on nail anatomy, females with Turner syndrome frequently have small hypoplastic nails. Shortened metacarpal bones, particularly the fourth metacarpal, are a frequent finding. The body shape of individuals with Turner syndrome is frequently quite broad and stocky, as the growth deficiency is more pronounced in the length of bones than in their width. Scoliosis is common in Turner syndrome, and is seen in 40% of girls without growth hormone treatment. Facial features associated with Turner syndrome include prominent ears, a low hairline, a webbed neck, a small chin with dental

malocclusion In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-193 ...

, and downslanting palpebral fissures (the opening between the eyelids). These are thought to be related to lymphedema during the fetal period, specifically to the presence and resorption of excess fluids in the head and neck region. Neck webbing is a particularly distinctive trait of Turner syndrome, leading to many neonatal diagnoses. The underlying etiology of neck webbing is related to prenatal blood flow issues, and even in populations without Turner's has broad health consequences; the rate of congenital heart disease in webbed neck is 150-fold higher than in the general population, while the feature is also associated with reduced height and minor developmental impairments. Some women with Turner syndrome have premature facial wrinkling. Acne is less common in teenage girls and women with Turner syndrome, though the reasons why are unclear. Baby Turner

Other physical features connected to the condition include long eyelashes, sometimes including an additional set of eyelashes, and unusual dermatoglyphics (fingerprints). Some women with Turner's report being unable to create fingerprint passwords due to hypoplastic dermatoglyphics. Unusual dermatoglyphics are common to chromosome anomalies and in the case of Turner's may be a consequence of fetal lymphedema. Keloid scars, or raised hypertrophic scars growing beyond the boundaries of the original wound, are potentially associated with Turner syndrome; however, the association is underresearched. Though traditional medical counselling on the topic urges conservatism about elective procedures such as ear piercing due to the risk of severe scarring, the actual consequences are unclear. Keloids in Turner syndrome are particularly frequent following surgical procedures to reduce neck webbing. Turner syndrome has been associated with unusual patterns of hair growth, such as patches of short and long hair. Armpit and pubic hair is often sparse, while arm and leg hair is often thick. Though armpit hair is reduced in amount and thickness, the pattern in which it is implanted in the skin is as in men, rather than as in women.

Cardiac

The basic anatomy of the bicuspid aortic valve

Approximately half of individuals with Turner syndrome have congenital heart defects. CHDs associated with Turner syndrome include bicuspid aortic valves (30%), coarctation of the aorta (15%), and abnormalities of the arteries in the head and neck. A rare but potentially fatal complication of heart defects in Turner syndrome is aortic dissection, where the inner layer of the aorta tears open. Aortic dissection is six times as common in females with Turner syndrome as the general population and accounts for 8% of all deaths in the syndrome. The risk is substantially increased for individuals with bicuspid aortic valves, who make up 95% of patients with aortic dissection compared to 30% of all Turner's patients, and coarctation of the aorta, who make up 90% and 15% respectively.

Coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves Ischemia, the reduction of blood flow to the myocardium, heart muscle due to build-up o ...

onsets earlier in life in women with Turner syndrome compared to controls, and mortality from cardiac events is increased. This is thought to be in part a function of the relationship between Turner syndrome and obesity; women with Turner syndrome have a higher percentage of body fat for their weight than control women, and their short stature makes weight control more difficult. Though coronary artery disease is frequently thought a disease of older adults, young women with Turner syndrome are more likely to develop the disease than their 46,XX peers. Treatment recommendations for women with Turner syndrome and coronary artery disease are as in the general population, but as Turner's increases the risk of type 2 diabetes, women with insulin resistance must weigh up the benefits of prophylactic or early statin treatment with the risk of diabetes.

Internal medicine

Turner syndrome is associated with a broad variety of health considerations, such as liver and kidney issues, obesity, diabetes, and hypertension. Liver dysfunction is common in women with Turner syndrome, with 50%–80% having elevated liver enzymes. Non-alcoholic fatty liver disease is increased in prevalence in Turner syndrome, likely related in part to both conditions' associations with obesity. Hepatic vascular diseases are also seen in the syndrome as an aspect of Turner syndrome's broader vascular and cardiac impacts. Primary biliary cholangitis is more common in 45,X0 than 46,XX women. An unclear association exists between estrogen replacement therapy and liver dysfunction in Turner syndrome; some studies imply estrogen therapy worsens such conditions, while others imply improvement.

Kidney issues, such as horseshoe kidney, are sometimes observed in Turner syndrome. Horseshoe kidney, where the kidneys are fused together in a U-shape, occurs in around 10% of Turner's cases compared to less than 0.5% of the general population. A missing kidney is observed in as many as 5% of individuals with Turner syndrome, compared to around 0.1% of the population. A

duplicated ureter Duplicated ureter or Duplex Collecting System is a congenital condition in which the ureteric bud, the embryological origin of the ureter, splits (or arises twice), resulting in two ureters draining a single kidney. It is the most common renal ...

, where two

ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional e ...

s drain a single kidney, occurs in as much as 20%–30% of the Turner syndrome population. Kidney malformations in Turner syndrome may be more common in mosaicism than in the full 45,X0 karyotype. Serious complications of the kidney anomalies associated with Turner syndrome are rare, although there is some risk of issues such as

obstructive uropathy Obstructive uropathy is a structural or functional hindrance of normal urine flow, sometimes leading to renal dysfunction (obstructive nephropathy). It is a very broad term, and does not imply a location or cause. Presentation Symptoms, less l ...

, where the flow of urine from the kidneys is blocked. Women with Turner syndrome are more likely than average to have high blood pressure; as many as 60% of women with the condition are hypertensive.

Isolated diastolic hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

often precedes systolic hypertension in the condition and may develop at a young age. Treatments for hypertension in Turner syndrome are as in the general population. Approximately 25%–80% of women with Turner syndrome have some level of insulin resistance, and a minority develop

type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urinati ...

. The risk of diabetes in Turner syndrome varies by karyotype and appears to be raised by specific deletions of the short arm of the X chromosome (Xp). One study found that while a relatively low 9% of women with Xq (long arm) deletions had type 2 diabetes, 18% of those with full 45,X0 karyotypes did, as well as 23% with Xp deletions. 43% of women with isochromosome Xq, who both lacked the short arm and had an additional copy of the long arm, developed type 2 diabetes. Though part of the diabetes risk in Turner syndrome is a function of weight control, some is independent; age- and weight-matched women with non-Turner's ovarian failure have a lower diabetes risk than in Turner syndrome. Growth hormone treatment plays an unclear role in diabetes risk, as does estrogen supplementation. The association between Turner syndrome and other diseases, such as cancer, is unclear. Overall, women with Turner syndrome do not appear more likely to develop cancer than women with 46,XX karyotypes, but the specific pattern of what cancers are highest risk seems to differ. The risk of

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or ...

appears lower in Turner's than in control women, perhaps due to decreased levels of estrogen. Neuroblastoma, a cancer of infancy and early childhood, has been reported in girls with Turner syndrome. Tumours of the nervous system, both the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

and the peripheral nervous system, are overrepresented amongst cancers in Turner syndrome. Furthermore, about 5.5% of Turner syndrome individuals have an extra, abnormal small supernumerary marker chromosome (sSMC) which consists of part of a Y chromosome. This partial Y chromosome-bearing sSMC may include the '' SRY'' gene located on the p arm of the Y chromosome at band 11.2 (notated as Yp11.2). This gene encodes the testis-determining factor protein (also known as sex-determining region Y protein). Turner syndrome individuals with this ''SRY'' gene-containing sSMC have a very real increased risk of developing

gonadal tissue neoplasm A gonadal tissue neoplasm is a tumor having any histology characteristic of cells or tissues giving rise to the gonads. These tissues arise from the sex cord and stromal cells. The tumor may be derived from these tissues, or produce them. Altho ...

s such as gonadoblastomas and in situ seminomas (also termed dysgerminomas to indicate that this tumor has the pathology of the testicular tumor, seminoma, but develops in ovaries). In one study, 34 Turner syndrome girls without overt evidence of these tumors were found at preventative surgery to have a gonadoblastoma (7 cases), dysgerminoma (1 case), or non-specific ''in situ'' gonadal neoplasm (1 case). Turner syndrome girls with this sSMC otherwise have typical features of the Turner syndrome except for a minority who also have hirsutism and/or clitoral enlargement. Surgical removal of the gonads has been recommended to remove the threat of developing these sSMC-associated neoplasms. Tuner syndrome individuals with an sSMC that lacks the ''SRY'' gene are not at an increased risk of developing these cancers.

Sensory

Hearing loss is common in Turner syndrome. Though at birth hearing is generally normal, chronic middle ear problems are frequent throughout childhood, which can cause permanent conductive hearing loss. In adulthood, sensorineural hearing loss occurs more often than in 46,XX women and at younger ages; though differing thresholds of hearing loss make it difficult to compare between studies, younger adult women with Turner syndrome are routinely found to have disproportionate rates of hearing issues, with sometimes up to half of women in their 20s and 30s having poor hearing. This hearing loss is progressive; at the age of 40, women with Turner syndrome have equivalent hearing loss to 46,XX women aged 60, on average. Cohort studies imply hearing loss may be more common in women who also have metabolic syndrome. The high prevalence of sensorineural hearing loss in Turner syndrome appears to be related to ''SHOX'' deficiency. Ocular and visual disorders are also increased in prevalence in Turner syndrome. More than half of individuals with Turner syndrome have some form of eye disorder. This may be a consequence of shared genes on the X chromosome in both eye and ovary development. Nearly half of cases have hyperopia or myopia, usually mild. Strabismus, or misalignment of the eye, occurs in around one-fifth to one-third of girls with Turner syndrome. As with strabismus outside the Turner's context, it may be treated with glasses, patching, or surgical correction. Esotropia, where the eye turns inwards, is more common than exotropia, where it turns outwards.

Ptosis Ptosis (from the Greek: πτῶσις 'falling', 'a fall', 'dropped') refers to droopiness or abnormal downward displacement of a body part or organ. Particular cases include: * Ptosis (eyelid) * Ptosis (chin) * Ptosis (breasts) * Visceroptosis, ...

, or a drooping eyelid, is a common facial manifestation of Turner syndrome; it usually has no appreciable impact on vision, but severe cases may limit visual range and require surgical correction. The rate of

red-green colourblindness Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color. It can impair tasks such as selecting ripe fruit, choosing clothing, and reading traffic lights. Color blindness may make some aca ...

in Turner syndrome is 8%, the same as in men. This is due to red-green colourblindness being an X-linked recessive condition; in people with a single X chromosome, whether normal males or Turner females, only a single mutated X is necessary for symptoms. Red-green colourblindness may be underdiagnosed in the Turner context, as the rarity of the condition in females reduces the likelihood of screening, and practitioners may not connect that the karyotype of Turner syndrome increases the risk from the female baseline.

Autoimmune

Women with Turner syndrome are two to three times as likely to develop autoimmune disorders as the general population. Specific autoimmune disorders linked to Turner syndrome include Hashimoto's disease, vitiligo, psoriasis and psoriatic arthritis, alopecia, and celiac disease.

Inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, Crohn's disease and ulcerative colitis being the principal types. Crohn's disease affects the small intestine and large intestine, as wel ...

is also common, while the prevalence of type 1 diabetes is unclear, though appears increased. Thyroid disease is common in Turner syndrome.

Hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. It can cause a number of symptoms, such as ...

is prevalent; 30%–50% of women with Turner syndrome have Hashimoto's disease, where the thyroid gland is slowly destroyed by an autoimmune reaction. By age 50, half of women with Turner syndrome have subclinical or clinical hypothyroidism.

Hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

and Graves' disease are also increased in prevalence, though more modestly. The Turner's presentation of hyperthyroidism is as in the general population, while the presentation of hypothyroidism is often atypical, with a mild early presentation yet a more severe progression. Women with isochromosome Xq are more likely to develop autoimmune thyroid disease than women with other forms of Turner syndrome. The risk of irritable bowel syndrome is increased around fivefold in Turner syndrome, and that of ulcerative colitis around fourfold. Celiac disease is also increased in prevalence, with around 4%–8% of Turner's patients having comorbid celiac disease compared to 0.5%–1% of the general population. Diagnosis of such conditions is difficult due to their nonspecific early symptoms. In the Turner's context, diagnosis may in particular be missed due to growth delay; such conditions cause growth delay and failure to thrive when they onset in childhood, but as girls with Turner syndrome already have such delay, symptoms may be overlooked and ascribed to the original condition. Alopecia areata, or recurrent patchy hair loss, is three times as common in Turner syndrome as the general population. Alopecia in the Turner syndrome context is frequently treatment-resistant, also seen in other chromosome aneuploidies such as

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with child development, physical growth delays, mild to moderate ...

. Psoriasis is common in Turner syndrome, although the precise prevalence is unclear. Turner's psoriasis may be related to growth hormone treatment, as psoriasis as a side effect of such therapies has been reported in patients without the karyotype. Psoriasis may progress to psoriatic arthritis, and this progression may be more common in Turner syndrome. Vitiligo has been reported in conjunction with Turner syndrome, but the risk is unclear and may be a side effect of increased clinical attention to autoimmune disease in this population.

Puberty

Histological sections of ovarian cortex from patients with TS

Puberty is delayed or absent in Turner syndrome. A 2019 literature review found that 13% of women with a 45,X0 karyotype could expect to experience spontaneous thelarche (breast development), while 9% would undergo spontaneous

menarche Menarche ( ; ) is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility. G ...

(beginning of menstruation). These numbers were higher in women with mosaic Turner's; 63% with 45,X0/46,XX karyotypes experienced spontaneous thelarche and 39% spontaneous menarche, while 88% with 45,X0/47,XXX (the presence of a

cell line) experienced spontaneous thelarche and 66% spontaneous menarche. Unexpectedly, women with Y-chromosome cells also had increased rates of thelarche and menarche compared to the 45,X0 baseline, at 41% and 19%. However, few women with trisomy X or Y-chromosome cell lines were covered in the review, impeding extrapolation from these results. 6% of women with Turner syndrome have regular menstrual cycles; the rest experience primary or secondary amenorrhea or other menstrual dysfunction. In girls with Turner syndrome who do not experience spontaneous puberty, exogenous estrogen is used to induce and maintain feminization. Estrogen replacement is recommended to begin at around age 11–12, although some parents prefer to delay the induction of puberty in girls with lower social and emotional preparedness. The dose of estrogen in induced puberty begins at 10% of adult estrogen levels and is steadily increased at six-month intervals, with a full adult dose attained two to three years after the beginning of treatment. Estrogen replacement may interfere with growth hormone therapy, due to the closing effects of estrogen on growth plates; individuals must weigh up their preferences for taller height versus greater feminization.

Fertility

Women with Turner syndrome are infertile. Only 2%–5% are capable of pregnancy without fertility treatment, most with mosaic karyotypes. Early in gestation, fetuses with Turner syndrome have a normal number of

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s in their developing ovaries, but this starts decreasingly rapidly as early as 18 weeks of pregnancy; by birth, girls with the condition have markedly reduced follicular counts. Women with Turner syndrome who wish to raise families but are incapable of conception with their own oocytes have the options of adoption or of pregnancy with donor eggs; the latter has a comparable success rate to donor pregnancy in women with 46,XX karyotypes. Pregnancy in Turner syndrome is inherently high-risk; the maternal death rate is 2%. Usually, estrogen replacement therapy is used to spur the growth of secondary sexual characteristics at the time when puberty should onset. While very few women with Turner syndrome menstruate spontaneously, estrogen therapy requires a regular shedding of the uterine lining ("withdrawal bleeding") to prevent its overgrowth. Withdrawal bleeding can be induced monthly, like menstruation, or less often, usually every three months, if the patient desires. Estrogen therapy does not make a woman with nonfunctional ovaries fertile, but it plays an important role in assisted reproduction; the health of the uterus must be maintained with estrogen if an eligible woman with Turner Syndrome wishes to use IVF (using donated oocytes). Especially in mosaic cases of Turner syndrome that contains Y-chromosome (e.g. 45,X/46,XY) due to the risk of development of ovarian malignancy (most common is gonadoblastoma) gonadectomy is recommended. Turner syndrome is characterized by primary amenorrhoea, premature ovarian failure (hypergonadotropic hypogonadism),

streak gonads Gonadal dysgenesis is classified as any congenital developmental disorder of the reproductive system in the male or female. It is the atypical development of the gonads in an embryo, with reproductive tissue replaced with functionless, fibrous t ...

and infertility (however, technology (especially oocyte donation) provides the opportunity of pregnancy in these patients). Failure to develop secondary sex characteristics (sexual infantilism) is typical.

Cognition

Neurodevelopmental

Individuals with Turner syndrome have normal intelligence. Verbal IQ is usually higher than performance IQ; one review of thirteen studies found an average verbal IQ of 101 compared to an average performance IQ of 89. People with Turner syndrome have normal intelligence, and demonstrate relative strengths in verbal skills, but may exhibit weaker nonverbal skills – particularly in arithmetic, select visuospatial skills, and processing speed. Turner syndrome does not typically cause

intellectual disability Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...

or impair cognition. However, learning difficulties are common among women with Turner syndrome, particularly a specific difficulty in perceiving spatial relationships, such as nonverbal learning disorder. This may also manifest itself as a difficulty with motor control or with mathematics. While it is not correctable, in most cases it does not cause difficulty in daily living. Most Turner syndrome patients are employed as adults and lead productive lives. Also, a rare variety of Turner syndrome, known as "Ring-X Turner syndrome", has about a 60% association with intellectual disability. This variety accounts for around 2–4% of all Turner syndrome cases.

Psychological

Social difficulties appear to be an area of vulnerability for young women. Counseling affected individuals and their families about the need to carefully develop social skills and relationships may prove useful in advancing social adaptation. Women with Turner syndrome may experience adverse psychosocial outcomes which can be improved through early intervention and the provision of appropriate psychological and psychiatric care. Genetic, hormonal, and medical problems associated with Turner syndrome are likely to affect psychosexual development of female adolescent patients, and thus influence their psychological functioning, behavior patterns, social interactions, and learning ability. Although Turner syndrome constitutes a chronic medical condition, with possible physical, social, and psychological complications in a woman's life, hormonal and estrogen replacement therapy, and assisted reproduction, are treatments that can be helpful for Turner syndrome patients and improve their quality of life. Research shows a possible association between age at diagnosis and increased substance use and depressive symptoms.

Prenatal

Despite the excellent postnatal prognosis, 99% of Turner syndrome conceptions are thought to end in miscarriage or stillbirth, and as many as 15% of all spontaneous abortions have the 45,X karyotype. Among cases that are detected by routine amniocentesis or chorionic villus sampling, one study found that the prevalence of Turner syndrome among tested pregnancies was 5.58 and 13.3 times higher, respectively, than among live neonates in a similar population.

Cause

Turner syndrome is caused by the absence of one complete or partial copy of the X chromosome in some or all the cells. The abnormal cells may have only one X ( monosomy) (45,X) or they may be affected by one of several types of

partial monosomy Aneuploidy is the presence of an abnormal number of chromosomes in a cell (biology), cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more ploidy#Haploid and monoploid, ...

like a deletion of the short p arm of one X chromosome (46, X,del(Xp)) or the presence of an isochromosome with two q arms (46,X,i(Xq)) Turner syndrome has distinct features due to the lack of pseudoautosomal regions, which are typically spared from X-inactivation. In mosaic individuals, cells with X monosomy (45,X) may occur along with cells that are normal (46,XX), cells that have partial monosomies, or cells that have a Y chromosome (46,XY). The presence of mosaicism is estimated to be relatively common in affected individuals (67–90%). The (46,X,i(Xq) isochromosome in the Turner syndrome is classified as an small supernumerary marker chromosome (sSMC). Two of the types of sSMCs in this syndrome contain parts of the genetic material from either an X or, much less frequently, Y chromosome and may or may not contain an '' XIST'' gene. In normal females, the ''XIST'' gene occurs on the X chromosome inherited from her mother but not on the X chromosome inherited from her father. The gene is not present on Y chromosomes and in normal females resides on and functions to inactivate many of the genes located on its own maternal but not the father's X chromosome. Turner syndrome females with (46,X,i(Xq) sSMC consisting of a partial X chromosome that does not contain the ''XIST'' gene express at least some of this sSMC's genetic material and therefore contain excesses of this material. In consequence, they have a more serious form of the Turner syndrome that ranges form moderately severe to extremely severe. The extremely severe cases have anencephaly (absence of a major portion of the brain, skull, and scalp), agenesis of the corpus callosum (lack of the thick tract of nerve fibers that connect the left and right

cerebral hemispheres The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...

), and complex heart deformities. Individuals with Turner syndrome that have partial X chromosome containing(46,X,i(Xq) sSMCs that have the ''XIST'' gene do not express this sSMC's genetic material and do not have the more severe manifestations of the syndrome.

Inheritance

In the majority of cases where monosomy occurs, the X chromosome comes from the mother. This may be due to a nondisjunction in the father.

Meiotic Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately res ...

errors that lead to the production of X with p arm deletions or abnormal Y chromosomes are also mostly found in the father. Isochromosome X or ring chromosome X on the other hand are formed equally often by both parents. Overall, the functional X chromosome usually comes from the mother. In most cases, Turner syndrome is a sporadic event, and for the parents of an individual with Turner syndrome the risk of recurrence is not increased for subsequent pregnancies. Rare exceptions may include the presence of a balanced

translocation Translocation may refer to: * Chromosomal translocation, a chromosome abnormality caused by rearrangement of parts ** Robertsonian translocation, a chromosomal rearrangement in pairs 13, 14, 15, 21, and 22 ** Nonreciprocal translocation, transfer ...

of the X chromosome in a parent, or where the mother has 45,X mosaicism restricted to her germ cells.

Diagnosis

Prenatal

Turner syndrome may be diagnosed by amniocentesis or chorionic villus sampling during pregnancy. Usually, fetuses with Turner syndrome can be identified by abnormal

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...

findings (''i.e.'', heart defect, kidney abnormality, cystic hygroma, ascites). In a study of 19 European registries, 67.2% of prenatally diagnosed cases of Turner syndrome were detected by abnormalities on ultrasound. 69.1% of cases had one anomaly present, and 30.9% had two or more anomalies. An increased risk of Turner syndrome may also be indicated by abnormal triple or quadruple maternal serum screen. The fetuses diagnosed through positive maternal serum screening are more often found to have a mosaic karyotype than those diagnosed based on ultrasonographic abnormalities, and conversely, those with mosaic karyotypes are less likely to have associated ultrasound abnormalities.

Postnatal

Turner syndrome can be diagnosed postnatally at any age. Often, it is diagnosed at birth due to heart problems, an unusually wide neck or swelling of the hands and feet. However, it is also common for it to go undiagnosed for several years, often until the girl reaches the age of puberty and fails to develop typically (the changes associated with puberty do not occur). In childhood, a short stature can be indicative of Turner syndrome. A test called a karyotype, also known as a chromosome analysis, analyzes the chromosomal composition of the individual. This is the test of choice to diagnose Turner syndrome.

Treatment

As a chromosomal condition, there is no cure for Turner syndrome. However, much can be done to minimize the symptoms. While most of the physical findings are harmless, significant medical problems can be associated with the syndrome. Most of these significant conditions are treatable with surgery and other therapies including hormonal therapy. * Growth hormone, either alone or with a low dose of androgen, will increase growth and probably final adult height. Growth hormone is approved by the U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

for treatment of Turner syndrome and is covered by many insurance plans. There is evidence that this is effective, even in toddlers. A 2019

systematic review A systematic review is a scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from published studies on t ...

comparing effects of adding oxandrolone to growth hormone treatment to growth hormone alone has found moderate-quality evidence that the addition of oxandrolone leads to an increase in final adult height of girls with Turner syndrome. When the same review assessed the effects of adding Oxandrolone to growth hormone treatment on speech, cognition and psychological status, the results were inconclusive due to very-low quality evidence. * Estrogen replacement therapy such as the birth control pill, has been used since the condition was described in 1938 to promote development of secondary sexual characteristics. Estrogens are crucial for maintaining good bone integrity, cardiovascular health and tissue health. Women with Turner syndrome who do not have spontaneous puberty and who are not treated with estrogen are at high risk for osteoporosis and heart conditions. * Modern reproductive technologies have also been used to help women with Turner syndrome become pregnant if they desire. For example, a donor egg can be used to create an embryo, which is carried by the Turner syndrome woman. * Uterine maturity is positively associated with years of estrogen use, history of spontaneous menarche, and negatively associated with the lack of current hormone replacement therapy.

Epidemiology

Turner syndrome occurs in between one in 2000 and one in 5000 females at birth. Approximately 99 percent of fetuses with Turner syndrome spontaneously terminate during the first trimester. Turner syndrome accounts for about 10 percent of the total number of spontaneous abortions in the United States.

History

The syndrome is named after Henry Turner, an endocrinologist from Illinois, who described it in 1938. In Europe, it is often called ''Ullrich–Turner syndrome'' or ''Bonnevie–Ullrich–Turner syndrome'' to acknowledge that earlier cases had also been described by European doctors Kristine Bonnevie and

Otto Ullrich Otto Ullrich (1894-1957) was a German pediatrician who identified and named Ullrich syndrome. Biography After Otto Ullrich studied medicine in Munich, he served as an assistant physician in the medical corps during World War I. Following the ...

. In Russian and USSR literature, it is called ''Shereshevsky–Turner syndrome'' to acknowledge that the condition was first described as hereditary in 1925 by the Soviet endocrinologist , who believed that it was due to the underdevelopment of the gonads and the anterior pituitary gland and was combined with congenital malformations of internal development. The first published report of a female with a 45,X karyotype was in 1959 by Charles Ford and colleagues in Harwell near

Oxford Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the Un ...

, and Guy's Hospital in London. It was found in a 14-year-old girl with signs of Turner syndrome.

Notes

References

External links

Turner Syndrome at the National Institute of Child Health and Human Development
*
Endocrine and Metabolic Diseases Information Service
{{Authority control Genodermatoses Growth disorders Rare syndromes Wikipedia medicine articles ready to translate Sex chromosome aneuploidies Syndromes affecting stature Syndromes affecting the heart Syndromes affecting the kidneys Intersex variations

Presentation

Physiological

Height

Physical features

Cardiac

Internal medicine

Sensory

Autoimmune

Puberty

Fertility

Cognition

Neurodevelopmental

Psychological

Prenatal

Cause

Inheritance

Diagnosis

Prenatal

Postnatal

Treatment

Epidemiology

History

See also

Notes

References

Further reading

External links