Paediatrics chapters
Turner syndrome
Complete or partial loss of one X chromosome in a girl: the karyotype types, the newborn and later features, short stature and ovarian failure, heart and kidney problems, and treatment with growth hormone and oestrogen.
- Turner syndrome is complete or partial loss of one X in a phenotypic female (about 1 in 2500 girls); half are 45,X, the rest mosaics or structural X changes; it is not linked to maternal age, and 45,X is the commonest chromosome finding in miscarriages.
- Look for lymphoedema of hands and feet and webbed neck in the newborn, short stature in childhood, and absent puberty with primary amenorrhoea (streak ovaries, high FSH) in adolescence; also coarctation, bicuspid aortic valve, horseshoe kidney, cubitus valgus, shield chest and hypothyroidism; intelligence is usually normal.
- Karyotype every unexplained short girl; treat with growth hormone early, oestrogen at puberty, correct heart lesions; most are infertile (donor eggs possible).
On this page
Overview
Turner syndrome is a disorder of girls caused by loss of all or part of one X chromosome (X monosomy). It is the only monosomy in which a conceptus can survive to term, although almost all such pregnancies miscarry. Its cardinal features are short stature and gonadal dysgenesis (streak ovaries), with characteristic physical signs, heart and kidney anomalies, and usually normal intelligence. Many girls are missed at birth because the signs are subtle.
Epidemiology and genetics
- About 1 in 2500 live-born females (Akbar); Nelson gives about 1 in 3200, and 1 in 2000-3000 in its endocrine chapter.
- 45,X is the commonest chromosome abnormality in spontaneous miscarriages; about 99% of 45,X embryos are lost.
- Not associated with advanced maternal age: the X (or Y) is thought to be lost after conception (mitotic error).
- In about 75% the missing sex chromosome came from the father (Akbar).
| Karyotype | Frequency (Nelson) | Notes |
|---|---|---|
| 45,X | About 50% | Classic form |
| Mosaic (45,X/46,XX; also 45,X/46,XY) | About 25% | Y material raises gonadoblastoma risk |
| Isochromosome Xq, 46,X,i(Xq) | About 15% | Two copies of the long arm, no short arm |
| Other X deletions | Remainder | Xp loss: short stature and malformations; Xq loss: gonadal failure |
Turner syndrome is the exception to the rule that chromosome disorders rise with maternal age. Down syndrome does; Turner syndrome does not.
Clinical features by age
About a third are diagnosed at birth (heart disease and physical signs), a third in childhood during work-up for short stature, and a third in adolescence when puberty fails (Nelson).
Newborn
- Lymphoedema (puffiness) of the hands and feet.
- Redundant skin at the back of the neck, from a cystic hygroma in fetal life.
- Webbed neck, low posterior hairline.
- Coarctation of the aorta or another left-heart lesion.
Childhood
- Short stature: the cardinal and most constant feature.
- Face: triangular, low-set mildly malformed ears, epicanthic folds, flat nasal bridge.
- Shield chest with widely spaced nipples.
- Cubitus valgus (wide carrying angle at the elbow).
- Scoliosis, congenital hip dislocation, patellar dislocation.
- Recurrent otitis media and sensorineural hearing loss.
- Strabismus, cataract; red-green colour blindness at male rates.
Adolescence
- Streak ovaries give oestrogen deficiency: no breast development, primary amenorrhoea, delayed or absent puberty.
- High FSH and LH (primary ovarian failure, hypergonadotropic hypogonadism).
- About 10% have some spontaneous puberty and may even be fertile (Nelson); almost all are infertile.
"Short, Shield, Streak, Swollen, Squeezed aorta": short stature, shield chest, streak ovaries, swollen hands and feet at birth, coarctation.
Associated problems
| System | Problem |
|---|---|
| Heart (about 45%) | Coarctation of the aorta (commonest), bicuspid aortic valve, hypoplastic left heart and other left-sided lesions, conduction abnormalities; later aortic root dilatation and dissection, especially in pregnancy |
| Kidney (over 50%) | Horseshoe kidney and other renal anomalies |
| Blood pressure | Hypertension is common (from coarctation or kidney anomaly) |
| Thyroid | Acquired hypothyroidism in about 15-30% (Akbar); about five times the population rate (Nelson) |
| Metabolism | Insulin resistance, type 2 diabetes |
| Gut | Coeliac disease, inflammatory bowel disease |
| Gonads | Gonadal dysgenesis; gonadoblastoma if Y material present |
| Ears and eyes | Otitis media, hearing loss, strabismus, cataract |
| Development | Usually normal intelligence; learning difficulties, and developmental delay in about 10% |
Turner = coarctation (and bicuspid aortic valve) on the left side of the heart. Check femoral pulses and blood pressure in every girl with Turner syndrome.
Diagnosis
- Karyotype confirms the diagnosis.
- Any girl who is short without another explanation should have a karyotype, even without typical features (both books).
- Supporting tests: high FSH and LH at pubertal age with low oestrogen; bone age.
- Then look for the associated problems: heart, kidneys, blood pressure, thyroid and hearing.
- Before birth: increased nuchal translucency or cystic hygroma and fetal oedema on ultrasound may suggest it; CVS or amniocentesis gives the karyotype.
A short girl with normal-looking features can still have Turner syndrome (especially a mosaic). Do not wait for a webbed neck.
Management
There is no cure, but most problems can be treated.
| Problem | Treatment |
|---|---|
| Short stature | Growth hormone, started young; increases growth rate and final height by a few inches |
| Absent puberty | Oestrogen replacement begun around the normal age of puberty (about 12 years), in low dose and increased gradually; a progestogen is added later to give regular withdrawal bleeds |
| Coarctation, valve disease | Cardiac surgery or intervention at the appropriate age; lifelong aortic surveillance |
| Hypertension | Treat the cause (coarctation, kidney) and give antihypertensives |
| Ear infections, hearing loss | Treat and assess hearing |
| Hypothyroidism, diabetes, coeliac disease | Screen regularly and treat |
| Infertility | Oestrogen does not restore fertility; donor eggs with assisted reproduction allow pregnancy, with close cardiac monitoring for aortic dissection |
- Psychological support and education about the condition are important.
- With treatment and support, most women with Turner syndrome lead a normal, healthy life with normal life expectancy (Nelson).
Turner versus Noonan syndrome
Noonan syndrome is sometimes called "pseudo-Turner" because it shares many features.
| Feature | Turner | Noonan |
|---|---|---|
| Cause | Loss of an X | Autosomal dominant single-gene defect |
| Sex | Girls only | Both sexes |
| Karyotype | 45,X or variant | Normal |
| Typical heart lesion | Coarctation, bicuspid aortic valve | Pulmonary valve stenosis, hypertrophic cardiomyopathy |
| Puberty and gonads | Streak ovaries, infertile | Delayed puberty; boys may have undescended testes and a small penis |
| Intellect | Usually normal | Mild intellectual disability in about a quarter |
| Shared | Short stature, webbed neck, low-set ears, chest deformity with wide-spaced nipples | Same |
Turner = left heart (coarctation); Noonan = right heart (pulmonary stenosis).
Expect: 45,X as the commonest karyotype and the mosaic and isochromosome variants; no maternal age effect; 45,X as the commonest finding in miscarriage; newborn lymphoedema and neck webbing; short stature as the cardinal sign and the rule to karyotype every unexplained short girl; coarctation and bicuspid aortic valve; horseshoe kidney; primary amenorrhoea with high FSH; normal intelligence; growth hormone and oestrogen treatment; infertility with donor eggs as the route to pregnancy and the risk of aortic dissection; gonadoblastoma with Y material; Noonan syndrome as the look-alike with pulmonary stenosis and a normal karyotype.
Quick revision
- Complete or partial X monosomy; about 1 in 2500 girls.
- 45,X about half; mosaics and isochromosome Xq the rest.
- No maternal age link; paternal X usually lost.
- Newborn: puffy hands and feet, neck skin folds, coarctation.
- Childhood: short stature, shield chest, cubitus valgus, webbed neck.
- Adolescence: streak ovaries, primary amenorrhoea, high FSH and LH.
- Heart about 45% (coarctation, bicuspid valve); kidneys over 50% (horseshoe).
- Hypothyroidism, type 2 diabetes, coeliac disease, hearing loss.
- Karyotype any short girl without a cause.
- GH for height, oestrogen at puberty, donor eggs for pregnancy.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Is intelligence affected in Turner syndrome?
Most girls have normal intelligence. Some have specific learning difficulties, and a small proportion have developmental delay.
Why is FSH high in Turner syndrome?
The ovaries are replaced by streaks that make little oestrogen. Without oestrogen feedback, the pituitary releases large amounts of FSH and LH.
Can a woman with Turner syndrome become pregnant?
A few with mosaicism have spontaneous puberty and fertility, but most are infertile. Pregnancy is possible with donor eggs, under close watch for aortic dissection.
Does growth hormone make girls with Turner syndrome reach normal height?
It improves growth rate and adds a few inches to final height, especially when started at a young age.