Turner Syndrome — Causes, Features, Diagnosis & Management Guide — Symptoms, Causes & Treatment | MyMedicPlus

Turner syndrome (TS) is a chromosomal condition affecting females, caused by the complete or partial absence of one X chromosome. The most common karyotype is 45,X (monosomy X), present in approximately 45% of cases. Other forms include 45,X/46,XX mosaicism (approximately 30%), 46,X,i(Xq) — isochromosome Xq (15%) — and structural X chromosome abnormalities. Turner syndrome occurs in approximately 1 in 2,500 live female births. It is the most common sex chromosome abnormality in females. Key features include short stature, gonadal dysgenesis (ovarian failure causing infertility in 95% of cases), and an increased risk of congenital heart and aortic anomalies. Intelligence is generally normal, though specific learning difficulties in visuospatial tasks and social cognition are common. Modern multidisciplinary management significantly improves outcomes and quality of life.

Turner syndrome results from errors in meiosis (cell division) or early mitosis leading to loss of all or part of the second sex chromosome. Complete monosomy X (45,X) arises from meiotic non-disjunction, most commonly in the paternal gamete (the paternal X chromosome is lost in approximately 70-80% of cases). Mosaic Turner syndrome (45,X/46,XX) results from errors in early post-fertilisation mitosis — the degree of mosaicism influences phenotypic severity, with some mosaic individuals having near-normal pubertal development. Unlike trisomies, Turner syndrome risk does not significantly increase with maternal age. The condition is not inherited in the traditional sense — it results from a sporadic chromosomal error. However, women with Turner syndrome who conceive (rare — requires IVF with donor eggs or, in mosaic cases, may use own eggs) are not at increased risk of having a child with Turner syndrome.

Prenatal features detectable on ultrasound: cystic hygroma (large fluid-filled mass at the neck), fetal hydrops, cardiac defects, and renal anomalies. In infancy: lymphoedema of the hands and feet (oedematous puffiness), webbing of the neck (pterygium colli), low hairline, broad chest with widely spaced nipples, and congenital heart defects — bicuspid aortic valve (30%) and coarctation of the aorta (10%). Short stature is universal — average adult height without treatment is approximately 143-147 cm (20 cm below average). Delayed or absent puberty due to gonadal dysgenesis — ovaries replaced by streak gonads that produce insufficient oestrogen, leading to primary amenorrhoea and infertility. Learning profile: normal verbal IQ but specific difficulties in visuospatial tasks, mathematics, and social cognition. Increased risks: hypothyroidism (30%), type 2 diabetes, aortic dilation and dissection, sensorineural hearing loss, celiac disease, and inflammatory bowel disease.

Prenatal diagnosis: via karyotype from chorionic villus sampling (CVS) or amniocentesis after abnormal first-trimester combined screening (elevated nuchal translucency) or structural anomalies on ultrasound. Cell-free fetal DNA (cfDNA/NIPT) can detect sex chromosome abnormalities from 10 weeks. Postnatal diagnosis: peripheral blood karyotype (minimum 30 cells to detect mosaicism). Fluorescence in situ hybridisation (FISH) and chromosomal microarray provide additional resolution when structural X abnormalities are suspected. At diagnosis: echocardiography and cardiac MRI (aortic assessment — bicuspid aortic valve, coarctation); renal ultrasound (horseshoe kidney in 30%); baseline hearing audiogram; thyroid function (TSH, anti-TPO — screening for autoimmune thyroiditis); glucose, lipids (cardiovascular risk). Bone age X-ray assesses growth potential. AMH and antral follicle count in mosaic Turner syndrome to assess residual ovarian function.

Growth hormone therapy: recombinant human GH (0.045-0.050 mg/kg/day) is initiated from early childhood (ideally age 4-6 years) and continued until final adult height is achieved — adds approximately 8-10 cm to final height above untreated projections. Oestrogen replacement therapy: initiated around age 11-12 to induce puberty, using low-dose transdermal or oral estradiol with gradual dose escalation over 2 years; progesterone is added after 2 years of oestrogen or at the first breakthrough bleed to allow cyclical withdrawal bleeds; continued until natural menopause age (approximately 50 years). Both GH and oestrogen have important roles in bone density — women with Turner syndrome have significantly increased osteoporosis risk requiring DXA monitoring. Fertility: over 95% are infertile; IVF with donor eggs gives reasonable success rates; egg cryopreservation at diagnosis should be discussed in mosaic patients with ovarian function. Cardiovascular: regular cardiac MRI (every 5-10 years) to monitor aortic diameter — aortic root above 2.5 cm/m2 warrants surgical consideration to prevent dissection.

Aortic dissection and rupture are the most life-threatening complications of Turner syndrome — the risk is approximately 6 times higher than the general population, even in the absence of aortic coarctation or bicuspid aortic valve; aortic root dilatation (indexed to body surface area above 2.5 cm/m²) warrants prophylactic surgical repair. Aortic dissection risk is further elevated during pregnancy, necessitating pre-conception cardiac assessment by MRI. Cardiovascular disease: bicuspid aortic valve (30%) is associated with aortic regurgitation and stenosis; coarctation of the aorta (10–15%) causes hypertension and requires surgical correction or balloon dilatation. Hypertension affects 25% of women with Turner syndrome and accelerates aortic risk. Osteoporosis develops from chronic oestrogen deficiency — women with Turner syndrome who do not receive adequate oestrogen replacement have significantly reduced bone mineral density and elevated fragility fracture risk, particularly vertebral and hip fractures by the fourth and fifth decades. Infertility: over 95% are infertile from premature ovarian failure; the emotional impact of infertility and loss of natural menopause is a significant psychological burden requiring specialist support. Hypothyroidism (autoimmune Hashimoto's thyroiditis) develops in 15–30% — annual TSH screening is essential. Type 2 diabetes and metabolic syndrome occur at substantially higher rates (2–4-fold elevated risk) even without obesity, from underlying insulin resistance associated with the 45,X karyotype. Progressive sensorineural hearing loss begins by the third decade in the majority and can significantly impair quality of life; regular audiometry from age 35 is recommended. Coeliac disease affects 4–8% of women with Turner syndrome — annual anti-TTG antibody screening is recommended. Inflammatory bowel disease (particularly Crohn's disease) is 10–fold more prevalent. Cognitive difficulties in mathematics and visuospatial tasks can affect employment and independence without appropriate educational support.

Turner syndrome cannot be prevented as it arises from random chromosomal events. Prenatal screening enables early diagnosis and preparation for multidisciplinary management. Long-term health surveillance is essential because of multiple associated medical risks. Annual monitoring: blood pressure (hypertension in 25%), thyroid function, fasting glucose, HbA1c (diabetes risk). Cardiac MRI every 5-10 years or more frequently if aortic diameter is above normal. Audiometry every 3-5 years (progressive sensorineural hearing loss from age 30). DXA bone density scan periodically. Celiac disease antibodies. Regular gynaecological review. Psychological and neurodevelopmental support for visuospatial and social difficulties. Turner Syndrome Society and support groups provide important peer support. Transition clinics facilitate transfer from paediatric to adult specialist care.

Seek urgent medical care for sudden severe chest, back, or abdominal pain in any woman with Turner syndrome — this may indicate aortic dissection, which is a life-threatening emergency occurring at higher rates in Turner syndrome (risk 6x population rate). Report any new palpitations, breathlessness, or chest discomfort promptly. Parents should seek genetic assessment if a female child has unexplained short stature, delayed puberty, webbed neck, oedematous hands or feet at birth, or learning difficulties with a specific visuospatial profile. Girls with known Turner syndrome should be seen by their multidisciplinary team (endocrinologist, cardiologist, audiologist, gynecologist) annually — missing surveillance visits increases the risk of missing serious complications. Women planning pregnancy should consult a reproductive specialist and cardiologist before attempting conception.