Turner's Syndrome
Summary
Turner Syndrome (TS) is a chromosomal disorder affecting females defined by the complete or partial irregularity of the X chromosome (most commonly 45,X). It is the most common sex chromosome abnormality in females (1:2500). The classic triad is Short Stature, Gonadal Dysgenesis (Streak Ovaries/Infertility), and Cardiac Defects (Left-sided obstructive lesions). Intelligence is usually normal. [1,2]
Clinical Pearls
The Puffy Neonate: A female neonate with lymphoedema of the hands and feet has Turner's until proven otherwise. This is caused by fetal lymphatic hypoplasia.
Murmurs Matter: Up to 30-50% have congenital heart disease. A murmur in a Turner's girl is Bicuspid Aortic Valve or Coarctation of the Aorta until cleared by Echo.
SHOX Gene: The short stature is specifically caused by haploinsufficiency of the SHOX gene on the short arm of the X chromosome. This is why Growth Hormone is effective.
Demographics
- Prevalence: 1 in 2000-2500 live female births. (99% of 45,X conceptions are spontaneously aborted).
- Genetics: Not associated with advanced maternal age.
Cytogenetics
- 45,X (Monosomy): 45%. (Classic).
- Mosaicism (e.g., 45,X/46,XX): 15-20%. (Milder phenotype, may be fertile).
- Structural Anomalies (Isochromosome Xq): Remaining cases.
Mechanisms
- Lymphatic Obstruction: Failure of lymphatics to form → Cystic Hygroma in utero → Webbed Neck (redundant skin) + Oedema.
- Haploinsufficiency: Loss of one copy of genes that escape X-inactivation (e.g. SHOX for bone growth).
- Germ Cell Apoptosis: Oocytes form but undergo accelerated apoptosis → Streak Ovaries (fibrous tissue) → Primary Amenorrhoea / Infertility.
| Condition | Features |
|---|---|
| Noonan Syndrome | "Male Turner's". PTPN11 mutation. Affects M & F. Right sided heart defects (Pulmonary Stenosis). |
| Leri-Weill Dyschondrosteosis | SHOX mutation alone. Mesomelic shortening (short forearms). |
| Constitutional Delay | Normal variants. Parents were "late bloomers". |
Neonatal
Childhood
Adolescence
Stigmata (The "Classic" look)
Genetic (Diagnostic)
- Karyotype: Gold standard (30 cells counted).
- FISH: For rapid diagnosis or mosaicism.
Screening (At Diagnosis)
- Cardiac: Echocardiogram (Coarctation, Bicuspid Valve, Aortic Root dilation). MRI Cardiac usually required in older children/adults for aortic visualisation.
- Renal Ultrasound: Horseshoe Kidney (30%), Duplex system.
- Endocrine: TSH (Autoimmune thyroiditis), HbA1c (Diabetes risk).
- Hearing: Audiology (Sensorineural dip).
Management Algorithm
DIAGNOSED TURNER SYNDROME
↓
MULTIDISCIPLINARY TEAM (MDT)
(Endo, Card, Gynae, Psych, ENT)
↓
GROWTH (Start Age ~4-5)
• Recombinant Human Growth Hormone (rhGH)
• Daily S/C injection
• Aim: Increase final height by 5-10cm
↓
PUBERTY (Start Age ~11-12)
• Low dose Oestrogen (Patches/Gel)
• Slowly titrate up over 2-3 years
• Add Progesterone (Cycling) once
bleeding starts or 2 years after Oestrogen
↓
ADULT TRANSITION
• HRT until age of natural menopause (50)
• Cardiac Surveillance (MRI Aorta every 5-10y)
• Fertility (Egg donation)
1. Growth
- GH Therapy: Initiated when growth failure detected (often age 4-6).
- Oxandrolone: Anabolic steroid sometimes added in late diagnosis to boost height (controversial).
2. Puberty & Fertility
- Oestrogen: Essential for breast development, bone health, and uterine growth.
- Pregnancy: High risk. Spontaneous pregnancy rare (2-5%). IVF with donor eggs is standard usually.
- Maternal Mortality: 2% risk of Aortic Dissection in pregnancy (Must screen aorta pre-conception).
3. Psychology
- Neurocognitive profile: Normal verbal IQ, but specific deficit in visuospatial processing and maths.
- Social immaturity / ADHD higher prevalence.
- Cardiovascular: Aortic Dissection (Leading cause of premature death). Hypertension.
- Autoimmune: Hypothyroidism (Hashimoto's - 30%), Coeliac Disease.
- Renal: UTI predisposition (Horseshoe kidney).
- Ears: Sensorineural hearing loss (conduction deafness early, sensorineural late).
- Bone: Osteoporosis (if HRT compliance poor).
- Life Expectancy: Slightly reduced (due to CV disease).
- Height: Mean untreated 143cm. Treated 150cm+.
- QoL: Generally good with support.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Turner Syndrome | Cincinnati Int. Consensus (2017) | Gold standard for care. Start GH early. Monitor Aorta. |
| Growth Hormone | NICE | Approved for Turner's. |
Landmark Evidence
1. Canadian/European Growth Hormone Trials
- Established the efficacy of rhGH in increasing final adult height by an average of 7-10 cm compared to untreated historical controls.
2. Aortic Dissection Registry
- Highlighted the critical risk of aortic dissection, even in patients with "normal" echocardiograms, mandating MRI surveillance.
What is Turner's Syndrome?
It is a genetic condition that only affects girls. Usually, girls have two "X" gene packages (Chromosomes). In Turner's, one of these X packages is missing or incomplete. It happens by chance when the baby is made and is not something the parents did wrong.
What does it mean for my daughter?
She will likely be shorter than other girls (unless we treat her) and may not start puberty on her own. She will likely need hormones to help her grow and develop. Her intelligence is usually normal.
Can she have children?
Most women with Turner's cannot have children naturally because their ovaries don't hold eggs properly. However, many can carry a pregnancy using donated eggs (IVF) when they are older.
What is the treatment?
Daily injections of Growth Hormone during childhood help her grow taller. In her teenage years, she will take Oestrogen (female hormone) to help her develop breasts and start periods.
Primary Sources
- Gravholt CH, et al. Clinical practice guidelines for the care of girls and women with Turner syndrome: proceedings from the 2016 Cincinnati International Turner Syndrome Meeting. Eur J Endocrinol. 2017.
- Bondy CA. Care of girls and women with Turner syndrome: a guideline of the Turner Syndrome Study Group. J Clin Endocrinol Metab. 2007.
Common Exam Questions
- Cardiology: "Murmur in Turner's?"
- Answer: Ejection Systolic (Bicuspid Valve) or Systolic radiating to back (Coarctation).
- Genetics: "Karyotype?"
- Answer: 45,X.
- Neonatology: "Swollen feet in female newborn?"
- Answer: Turner's (Lymphoedema).
- Renal: "Kidney anomaly?"
- Answer: Horseshoe Kidney.
Viva Points
- Noonan's Syndrome: Often called "Male Turner's" because they look similar (webbed neck, short), but Noonan's is Autosomal Dominant (affects boys too) and has Right sided heart lesions (Pulmonary Stenosis), whereas Turner's has Left sided (Aortic).
- Pregnancy Risk: Why is pregnancy dangerous? Aortic Dissection. Blood volume increases in pregnancy, stressing the already vulnerable aorta.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.