Turner Syndrome (Child)

1. Overview

Turner syndrome (TS) is a chromosomal disorder affecting phenotypic females, characterised by complete or partial absence of one X chromosome. [1] It represents the most common sex chromosome abnormality in females with a prevalence of approximately 1 in 2,000-2,500 live female births, though an estimated 99% of 45,X conceptions result in spontaneous first-trimester miscarriage. [2,3]

The condition was first comprehensively described by Henry Turner in 1938, though earlier descriptions by Ullrich in 1930 led to the alternative eponym Ullrich-Turner syndrome. [4] The genetic basis—monosomy X—was discovered by Ford and colleagues in 1959 using karyotype analysis. [5]

Turner syndrome is clinically heterogeneous, with manifestations ranging from severe to subtle depending on karyotype and mosaicism. The cardinal features constitute a classical triad: short stature, gonadal dysgenesis (with consequent primary amenorrhoea and infertility), and congenital cardiovascular anomalies (particularly left-sided obstructive lesions). [6] Additional features include characteristic dysmorphic features, renal anomalies, and increased risk of autoimmune disorders. Despite these challenges, cognitive development is typically normal, with average to above-average verbal intelligence, though specific deficits in visuospatial processing and mathematical reasoning are common. [7]

Early diagnosis and multidisciplinary management significantly improve outcomes. Modern treatment with growth hormone therapy increases final adult height by 5-10 cm, while oestrogen replacement therapy enables normal pubertal development, bone health, and cardiovascular protection. [8,9] With appropriate care, women with Turner syndrome can expect good quality of life, though life expectancy remains slightly reduced primarily due to cardiovascular complications. [10]

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2. Epidemiology

Incidence and Prevalence

Turner syndrome accounts for approximately 10% of all spontaneous first-trimester miscarriages, representing one of the most common chromosomal causes of early pregnancy loss. [11] The vast majority of affected conceptuses are non-viable, with only those who are mosaic or have less severe karyotypes surviving to birth.

Demographics

Age Distribution:

• Diagnosis increasingly made prenatally through NIPT or amniocentesis (20-30% of current cases) [13]
• Neonatal presentation: 15-20% (lymphoedema, cardiac anomalies)
• Childhood: 30-40% (short stature, developmental concerns)
• Adolescence: 30-40% (delayed puberty, primary amenorrhoea)

Maternal Age: Unlike Down syndrome, Turner syndrome shows no association with advanced maternal age. [14] The missing or abnormal X chromosome is equally likely to be of maternal or paternal origin.

Ethnicity: Affects all ethnic groups equally with no significant geographic or racial variation in prevalence. [3]

Risk Factors

Turner syndrome arises from random chromosomal errors during meiosis or early mitotic divisions. There are no established modifiable risk factors. [14] Recurrence risk in subsequent pregnancies is not increased above population baseline (less than 1%), making it a sporadic condition rather than inherited.

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3. Aetiology & Pathophysiology

Cytogenetic Mechanisms

Turner syndrome results from complete or partial loss of one X chromosome. The karyotypic distribution is: [15]

Parental Origin: The single X chromosome may be maternal (70-80% of cases) or paternal (20-30%). Phenotype severity does not correlate with parental origin. [16]

Molecular Pathophysiology

The clinical manifestations of Turner syndrome result from haploinsufficiency of genes that normally escape X-inactivation. Key pathogenic mechanisms include: [17]

1. Short Stature - SHOX Gene Haploinsufficiency

The SHOX gene (Short stature HOmeoboX-containing gene) is located on the pseudoautosomal region (PAR1) of the short arm of the X chromosome (Xp22.33). [18] This gene normally escapes X-inactivation, so two functional copies are present in normal females (one per X chromosome).

• Function: SHOX encodes a transcription factor crucial for chondrocyte differentiation and bone growth, particularly in long bones
• Haploinsufficiency effect: Loss of one copy leads to:
  • Reduced longitudinal growth of long bones
  • Mesomelic limb shortening (disproportionate shortening of forearms and lower legs)
  • Madelung deformity (distal radial abnormality) in some cases
• Growth pattern: Normal birth length, progressive deceleration through childhood, absent pubertal growth spurt
• Final height: Mean untreated adult height 143-147 cm (20-25 cm below population mean) [19]

This explains why growth hormone therapy is effective despite normal GH-IGF-1 axis—the treatment partially compensates for SHOX haploinsufficiency through enhanced chondrocyte proliferation.

2. Gonadal Dysgenesis - Accelerated Oocyte Apoptosis

The mechanism of ovarian failure in Turner syndrome involves: [20]

• Prenatal: Primordial germ cells migrate normally and oocytes form initially
• Fetal period: Accelerated apoptosis (programmed cell death) of oocytes begins
• Birth: Streak ovaries containing fibrous tissue with minimal or no follicles
• Childhood: Residual follicles (if present) undergo continued atresia
• Adolescence: Insufficient follicles for spontaneous puberty (less than 1% with 45,X; 10-20% with mosaicism)

The X chromosome genes critical for oocyte survival that are lost include genes involved in DNA repair and cell cycle regulation. Loss of two functional X chromosomes is essential for maintaining the ovarian reserve.

Spontaneous Puberty:

• 12-21% of all Turner syndrome patients (higher in mosaic karyotypes) [21]
• Transient in most cases; premature ovarian insufficiency develops in early 20s
• 2-5% may achieve spontaneous pregnancy (almost exclusively mosaics)

3. Lymphatic Dysplasia - Developmental Defect

Congenital lymphatic hypoplasia results in: [22]

• In utero: Cystic hygroma formation (enlarged nuchal translucency on prenatal ultrasound)
• Birth: Lymphoedema of hands and feet ("puffy baby")
• Infancy: Resolution as collateral lymphatic channels develop
• Residual features: Webbed neck (pterygium colli), low posterior hairline—result from nuchal oedema resolution

4. Cardiovascular Anomalies - Altered Developmental Pathways

Congenital heart disease occurs in 30-50% of Turner syndrome patients: [23,24]

Left-sided obstructive lesions (characteristic):

• Bicuspid aortic valve (30%): Most common—increased risk of aortic stenosis and regurgitation
• Coarctation of the aorta (10-15%): Juxtaductal narrowing—check femoral pulses at every examination
• Hypoplastic left heart (rare): Most severe presentation
• Aortic root dilatation: Progressive; risk of dissection (leading cause of premature death)

Mechanism: Altered haemodynamic flow during cardiac development due to:

• Abnormal lymphatic drainage affecting cardiac morphogenesis
• Disturbed extracellular matrix formation
• Possible genetic factors (haploinsufficiency of cardiac developmental genes)

Ongoing Risk: Even structurally normal aortas show:

• Aortic stiffness and reduced compliance
• Progressive aortic dilatation throughout life
• 3-fold increased risk of aortic dissection (primarily Type A) [10,25]

5. Renal Anomalies

Structural renal malformations occur in 30-40%: [26]

• Horseshoe kidney (10-15%): Fusion of lower poles
• Duplex collecting system (15%): Increased UTI risk
• Renal agenesis (unilateral): Rare but significant
• Pelvic kidney, malrotation: Other variants

These result from disrupted renal embryogenesis during weeks 4-8 of gestation.

6. Autoimmune Predisposition

Increased autoimmune disease prevalence (mechanism unclear): [27]

• Hypothyroidism (Hashimoto's thyroiditis): 15-30%
• Coeliac disease: 4-6% (vs 1% general population)
• Inflammatory bowel disease: 2-3× increased risk
• Type 1 diabetes: Slightly increased

Postulated mechanisms include altered immune regulation and thymic hypoplasia.

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4. Clinical Presentation

Presentation by Age

Prenatal (Increasingly Common)

Ultrasound findings: [13]

• Increased nuchal translucency (> 3.5 mm at 11-14 weeks)
• Cystic hygroma (large septated posterior neck mass)
• Non-immune hydrops fetalis
• Coarctation of aorta or left heart hypoplasia
• Renal anomalies

NIPT screening: May detect sex chromosome aneuploidy, prompting diagnostic amniocentesis

Karyotype: Diagnostic amniocentesis confirms diagnosis

Neonatal (15-20% diagnosed)

Classic triad: [22]

1. Lymphoedema of dorsum of hands and feet ("puffy hands and feet")
2. Webbed neck (pterygium colli) or excess nuchal skin
3. Cardiac murmur (if coarctation or valve abnormality present)

Additional features:

• Low birth weight (mean 2,800 g despite term gestation)
• Narrow, hyperconvex nails (spoon-shaped)
• Low posterior hairline
• Feeding difficulties
• Recurrent otitis media

Red Flag: Absent or reduced femoral pulses → investigate for coarctation immediately with echocardiography

Infancy and Early Childhood (5-10% diagnosed)

• Growth failure: Deceleration of growth velocity (crossing down centile lines)
• Recurrent otitis media (60-80%): Due to Eustachian tube dysfunction and facial bone abnormalities [28]
• Feeding difficulties: May require NG feeding support
• Hearing loss: Conductive (early) → sensorineural (later)

Late Childhood (30-40% diagnosed)

Presentation: Referral for short stature (most common presentation)

• Growth velocity less than 4 cm/year
• Height less than 3rd centile or crossing centiles downward
• Disproportion (short limbs relative to trunk)
• No pubertal growth spurt

Associated features:

• Multiple pigmented naevi
• Recurrent otitis media
• Mild learning difficulties (specific, not global)

Adolescence (30-40% diagnosed)

Presentation: Delayed puberty or primary amenorrhoea

• No breast development by age 13 (absent thelarche)
• No menarche by age 15-16
• Infantile external genitalia
• Elevated gonadotrophins (FSH, LH)

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Dysmorphic Features (Variable Presence)

The "classic Turner syndrome phenotype" is highly variable—many patients, especially mosaics, have minimal or no dysmorphic features. [29]

Clinical Pearl: The presence or absence of dysmorphic features does not predict severity of medical complications (cardiac, renal, autoimmune).

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Neurocognitive Profile

Intelligence: [7,30]

• Global IQ: Usually normal (mean IQ 90-100, similar to general population)
• Verbal IQ: Often above average (relative strength)
• Performance IQ: Below average (relative weakness)

Specific deficits:

• Visuospatial processing: Difficulty with spatial relationships, mental rotation
• Executive function: Planning, organisation, working memory
• Mathematics: Arithmetic difficulties common (dyscalculia)
• Social cognition: Difficulty reading social cues, facial recognition deficits

Associated conditions:

• ADHD: 3-4× increased prevalence (20-25%)
• Anxiety: Social anxiety particularly common
• Autism spectrum traits: Mild increase

Educational implications: Most attend mainstream schools with targeted support for mathematics and visuospatial tasks.

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5. Differential Diagnosis

Turner syndrome should be considered in the differential diagnosis of:

1. Short Stature in Girls

2. Primary Amenorrhoea

3. Neonatal Lymphoedema

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6. Investigations

Diagnostic Investigations

Karyotype (Gold Standard)

Indications: [15]

• Any girl with unexplained short stature (less than 3rd centile)
• Primary amenorrhoea or delayed puberty (no breast development by 13)
• Neonatal lymphoedema in female infant
• Prenatal diagnosis: increased NT, cystic hygroma, coarctation

Method:

• Peripheral blood lymphocyte culture
• 30 cells must be counted to exclude low-level mosaicism
• G-banding technique visualises chromosome structure

Results:

• 45,X (monosomy): Classic
• 45,X/46,XX (mosaic): Variable phenotype
• 46,X,i(Xq) (isochromosome): Loss of short arm
• 46,X,del(Xp) or del(Xq): Partial deletions
• Y chromosome material: Requires gonadectomy (gonadoblastoma risk 12-30%) [31]

Limitations: May miss very low-level mosaicism; consider skin fibroblast karyotype if high clinical suspicion despite normal blood karyotype

FISH (Fluorescence In Situ Hybridisation)

• Rapid preliminary result (24-48 hours vs 7-10 days for full karyotype)
• Useful in neonatal period when rapid diagnosis needed
• Must be followed by formal karyotype

Array CGH (Comparative Genomic Hybridisation)

• Detects small deletions/duplications not visible on karyotype
• Useful if atypical features suggest partial X chromosome deletion

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Screening Investigations at Diagnosis

Once Turner syndrome is diagnosed, comprehensive screening for associated anomalies is essential:

Cardiovascular Assessment

Baseline investigations: [24]

1. Echocardiography (MANDATORY)

   • Assess for bicuspid aortic valve (30%)
   • Coarctation of aorta (10-15%)
   • Ventricular septal defect (VSD)
   • Partial anomalous pulmonary venous drainage
   • Aortic root dimensions (measure aortic root diameter indexed to BSA)

2. 4-limb blood pressure (clinical screening for coarctation)

   • Difference > 20 mmHg upper vs lower limbs suggests coarctation
   • Hypertension common even without structural lesions

3. Cardiac MRI (increasingly recommended)

   • Indications: Poor echocardiographic windows, abnormal aortic dimensions, surgical planning
   • Superior visualisation of:
     • Aortic arch anatomy
     • Coarctation severity
     • Aortic root and ascending aorta
     • Partial anomalous pulmonary venous drainage

Follow-up:

• Repeat echo every 3-5 years in childhood
• Transition to cardiac MRI in adolescence/adulthood for aortic surveillance

Renal Assessment

Renal ultrasound: [26]

• Detects structural anomalies in 30-40%
• Horseshoe kidney (10-15%)
• Duplex collecting systems
• Pelvic or ectopic kidney
• Unilateral renal agenesis

Renal function tests:

• Usually normal
• Monitor if structural anomalies present

Urine analysis:

• Baseline to detect asymptomatic UTI (more common with duplex systems)

Endocrine Assessment

Thyroid function: [27]

• TSH, free T4
• Anti-thyroid peroxidase (anti-TPO) antibodies
• 15-30% develop Hashimoto's thyroiditis
• Repeat annually lifelong

Gonadotrophin levels:

• FSH, LH elevated (> 40 IU/L) indicating ovarian failure
• Useful to confirm diagnosis in adolescents
• Not necessary in young children (prepubertal levels normally low)

Glucose metabolism:

• Fasting glucose or HbA1c
• Increased risk of impaired glucose tolerance and Type 2 diabetes
• Screen annually from adolescence

Growth hormone axis (if considering treatment):

• Usually normal
• IGF-1, IGFBP-3 typically normal
• GH stimulation testing not routinely required (diagnosis is indication for therapy)

Audiology Assessment

Hearing evaluation: [28]

• Frequency: Baseline, then annually through childhood
• Findings:
  • "Conductive hearing loss (childhood): Due to recurrent otitis media"
  • "Sensorineural hearing loss (progressive): High-frequency loss from adolescence"
  • 40-60% will have hearing impairment by adulthood

Management:

• Grommets if chronic otitis media with effusion
• Hearing aids if sensorineural loss significant

Coeliac Screening

Tissue transglutaminase (tTG) IgA + Total IgA:

• 4-6% prevalence (vs 1% general population)
• Screen at diagnosis, repeat every 2-3 years
• If positive → duodenal biopsy for confirmation

Liver Function

Baseline LFTs:

• 30-50% have mildly elevated transaminases (ALT, AST)
• Usually non-progressive, benign
• Monitor; consider abdominal ultrasound if persistent elevation

Bone Density (Later Childhood/Adolescence)

DEXA scan:

• Assess bone mineral density
• Risk of osteoporosis if delayed oestrogen replacement or poor compliance with HRT
• Repeat in late adolescence and adulthood

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Monitoring Investigations

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7. Management

Management of Turner syndrome requires lifelong multidisciplinary care coordinated through a specialist centre.

Multidisciplinary Team

Core team members:

• Paediatric endocrinologist (lead)
• Paediatric cardiologist
• Clinical geneticist
• Gynaecologist (transition planning)
• Audiologist
• Clinical psychologist
• Specialist nurse coordinator

Additional specialists as needed:

• ENT surgeon (grommets, hearing aids)
• Orthopaedic surgeon (skeletal abnormalities)
• Reproductive medicine specialist (fertility counselling)
• Adult endocrinologist and cardiologist (transition)

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1. Growth Hormone Therapy

Rationale: Compensates for SHOX haploinsufficiency; increases final adult height by average 5-10 cm (range 3-16 cm). [8,32]

Indications

• Diagnosis of Turner syndrome is sufficient indication (no GH deficiency testing required)
• Growth velocity less than 4-5 cm/year
• Height less than 3rd centile or crossing centiles downward

Timing

• Optimal start: Age 4-6 years
• Earlier initiation (from age 2) under investigation but not yet standard
• Later diagnosis: Still beneficial even if started in late childhood/early adolescence, though gains are smaller

Dosing

• Dose: 0.045-0.05 mg/kg/day subcutaneous injection (higher than GH deficiency dosing)
• Route: Daily subcutaneous injection (usually evening)
• Duration: Continue until:
  • Bone age ≥14 years, OR
  • Growth velocity less than 2 cm/year, OR
  • Epiphyses fused

Monitoring

• Height velocity: Every 3-6 months
• Bone age: X-ray left hand/wrist annually
• IGF-1: Monitor to ensure levels in upper-normal range (avoid supraphysiological levels)
• Glucose metabolism: Annual HbA1c or fasting glucose (GH can reduce insulin sensitivity)
• Thyroid function: Can unmask hypothyroidism

Expected Outcomes

• Untreated final height: 143-147 cm
• Treated final height: 148-158 cm (average ~152 cm)
• Gain of 5-10 cm on average vs untreated predicted height
• Maximum benefit if started early and continued until near-final height

Adjunctive Therapy

Oxandrolone (anabolic steroid):

• Occasionally added in late childhood (age > 9) if suboptimal GH response
• Dose: 0.03-0.05 mg/kg/day
• May add additional 1-2 cm height gain
• Risks: Virilisation (deepening voice, hirsutism), early epiphyseal closure
• Use controversial; not routinely recommended in UK

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2. Oestrogen Replacement Therapy

Rationale: Induce and maintain secondary sexual characteristics, optimise bone health, cardiovascular protection, uterine development (enables pregnancy via egg donation), psychological well-being. [9,33]

Indications

• Primary ovarian insufficiency (> 95% of Turner syndrome)
• Absence of spontaneous puberty by age 11-12 years
• Elevated FSH (> 40 IU/L) confirming ovarian failure

Timing

• Optimal start: Age 11-12 years (physiological age of puberty onset)
• Enables peer-appropriate pubertal development
• Critical for bone density accrual during adolescence
• Earlier start may compromise final height (closes growth plates)—balance with growth hormone therapy

Preparation

Low-dose oestrogen to mimic natural puberty:

• Transdermal (patches or gel) preferred over oral
  • More physiological delivery
  • Avoids first-pass hepatic metabolism
  • Lower thrombotic risk

Dosing regimen (gradual dose escalation over 2-3 years): [33]

Alternative (oral):

• Ethinylestradiol 2-5 mcg daily initially, increasing to 10-20 mcg daily
• Less preferred due to hepatic effects and less physiological

Progesterone Addition

Timing: Add progesterone after:

• Breakthrough bleeding occurs (suggests adequate endometrial development), OR
• 2 years of oestrogen therapy

Purpose:

• Endometrial protection (prevent hyperplasia)
• Induce regular withdrawal bleeds

Regimen:

• Cyclical: Medroxyprogesterone acetate 5-10 mg days 1-12 of each month, OR
• Micronised progesterone 100-200 mg days 1-12 of each month
• Withdrawal bleed occurs after progesterone stops

Monitoring

• Tanner staging: Assess breast development every 6-12 months (aim for gradual progression)
• Bone density: DEXA scan in late adolescence
• Cardiovascular risk: Blood pressure, lipids
• Compliance: Regular clinic review; many adolescents struggle with adherence
• Psychological support: Address body image, fertility concerns

Duration

• Lifelong until age of natural menopause (~50 years)
• Transition from "oestrogen replacement" to standard HRT in adulthood
• Critical for bone health and cardiovascular protection

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3. Spontaneous Puberty Surveillance

In mosaic Turner syndrome (particularly 45,X/46,XX), spontaneous puberty occurs in 12-21%: [21]

Management approach:

• Watch and wait if signs of spontaneous puberty (breast budding, growth acceleration) by age 12
• Delay oestrogen replacement to see if endogenous puberty progresses
• Risk: Most will develop premature ovarian insufficiency in early 20s (even if initially spontaneous)
• Fertility counselling: Spontaneous pregnancy possible but rare; if desired, consider early reproductive planning (egg freezing controversial but occasionally considered)

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4. Cardiovascular Management

Baseline and Surveillance

• Echocardiography: Baseline, then every 3-5 years
• Cardiac MRI: Transition to MRI in adolescence/adulthood for aortic surveillance
• Blood pressure: Every clinic visit; manage hypertension aggressively

Specific Lesions

Bicuspid Aortic Valve (30%):

• Antibiotic prophylaxis for dental procedures no longer routinely recommended (per current guidelines)
• Monitor for progressive stenosis or regurgitation
• Surgical intervention if severe (valve repair/replacement)

Coarctation of Aorta (10-15%):

• Diagnosis: Upper limb hypertension, weak/absent femoral pulses, > 20 mmHg arm-leg BP gradient
• Management:
  • Balloon angioplasty (primary treatment in older children/adolescents)
  • Surgical repair (neonatal/infant presentations or complex anatomy)
  • Stenting (recurrent coarctation)
• Follow-up: Lifelong; risk of recoarctation, persistent hypertension, aneurysm formation

Aortic Root Dilatation:

• Surveillance: Measure aortic root diameter indexed to BSA
• Threshold: Aortic size index (ASI) > 2 cm/m² concerning
• Management:
  • Beta-blockers or ACE inhibitors may slow progression (controversial; limited evidence)
  • Surgical aortic root replacement if severe dilatation (ASI > 2.5 cm/m² or rapid progression)

Pregnancy Counselling (Later in Life)

• Aortic dissection risk: 2% maternal mortality in pregnancy due to dissection [34]
• Contraindications to pregnancy:
  • Aortic size index > 2.5 cm/m²
  • Bicuspid aortic valve with significant regurgitation/stenosis
  • Severe coarctation
• Pre-pregnancy: Mandatory cardiac MRI and cardiology assessment
• If pregnancy proceeds: High-risk obstetric and cardiology surveillance throughout

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5. Otologic Management

Recurrent otitis media: [28]

• Common in childhood (60-80%)
• Management:
  • Prompt antibiotic treatment
  • Grommets (tympanostomy tubes) if chronic otitis media with effusion
  • Reduces conductive hearing loss impact

Sensorineural hearing loss:

• Progressive from adolescence (high-frequency loss)
• Management: Hearing aids if interfering with function
• Annual audiometry to detect early changes

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6. Psychological and Educational Support

Neurocognitive support: [30]

• Mathematics: Targeted support for dyscalculia
• Visuospatial tasks: Occupational therapy, specific interventions
• Executive function: Organisational skills training

Psychological support:

• Body image: Short stature, delayed puberty impact self-esteem
• Social skills: Social cognition deficits may require intervention
• Fertility counselling: Address infertility grief and alternative family planning options

ADHD screening and management:

• 20-25% prevalence
• Standard ADHD medications (methylphenidate, atomoxetine) if diagnosed

School support:

• Most attend mainstream schools
• Education, Health and Care Plan (EHCP) if significant needs
• Peer awareness to reduce bullying related to short stature/appearance

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7. Other Medical Management

Hypothyroidism (15-30%):

• Annual TSH screening
• Levothyroxine replacement if diagnosed

Coeliac disease (4-6%):

• Screening every 2-3 years
• Gluten-free diet if diagnosed

Type 2 diabetes prevention:

• Lifestyle advice (diet, exercise)
• Monitor glucose/HbA1c annually
• Metformin if impaired glucose tolerance develops

Osteoporosis prevention:

• Adequate calcium and vitamin D intake
• Weight-bearing exercise
• Oestrogen replacement (most important)
• DEXA scanning and bisphosphonates if osteoporotic despite treatment

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8. Transition to Adult Care

Timing: Age 16-18 years (varies by centre)

Adult services required:

• Adult endocrinology (HRT continuation)
• Adult cardiology (aortic surveillance)
• Gynaecology/reproductive medicine (fertility, sexual health)
• Audiology
• Psychology

Key transition issues:

• HRT adherence: Often poor in young adults; emphasise lifelong need
• Cardiovascular surveillance: Critical to continue MRI/echo surveillance
• Fertility counselling: Egg donation, adoption, or choosing to be child-free
• Sexual health: Education regarding relationships, contraception (if spontaneous pregnancy possible in mosaics)

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8. Complications

Cardiovascular Complications

Leading cause of premature death: Aortic dissection, typically Type A (ascending aorta). [10,25]

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Reproductive and Endocrine Complications

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Renal and Gastrointestinal Complications

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Neurological and Sensory Complications

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Gonadoblastoma Risk

In patients with Y chromosome material detected on karyotype (5-10% of Turner syndrome):

• Risk: 12-30% risk of gonadoblastoma (malignant germ cell tumour) [31]
• Management: Prophylactic bilateral gonadectomy recommended
• Timing: Once diagnosis confirmed; usually performed laparoscopically in childhood/adolescence

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9. Prognosis

Life Expectancy

• Slightly reduced compared to general population [10]
• Mean reduction: ~10-13 years
• Leading causes of premature death:
  1. Aortic dissection/rupture (responsible for ~40% of excess mortality)
  2. Cardiovascular disease (coronary artery disease, stroke)
  3. Congenital heart disease complications

Survival rates:

• Age 50: ~90% (vs ~96% general population)
• Age 70: ~70% (vs ~85% general population)

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Height Outcomes

Predictors of better height outcome:

• Earlier GH therapy initiation
• Longer treatment duration
• Higher parental height
• Mosaic karyotype (45,X/46,XX)

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Fertility Outcomes

• Spontaneous pregnancy: 2-5% overall; almost exclusively in mosaics
• IVF with donor eggs: Success rates similar to age-matched controls (40-50% per cycle in women less than 35)
• Adoption: Alternative family-building option
• Child-free: Valid personal choice

Pregnancy risks (if achieved):

• 30% miscarriage rate
• 20-30% preterm delivery
• 2% maternal mortality (aortic dissection)
• Requires high-risk obstetric and cardiology care

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Quality of Life

With optimal multidisciplinary care: [35]

• Educational attainment: Most complete mainstream education; many pursue higher education
• Employment: Employment rates similar to general population
• Relationships: Most form long-term relationships; marriage rates slightly lower
• Psychological well-being: Increased risk of anxiety and depression, but most adapt well with support

Factors associated with better QoL:

• Early diagnosis and treatment
• Good HRT adherence
• Psychological support
• Support group involvement (Turner Syndrome Support Society)

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10. Prevention & Screening

Primary Prevention

Turner syndrome arises from random chromosomal errors; there are no known preventable risk factors. [14]

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Prenatal Screening

Non-Invasive Prenatal Testing (NIPT):

• Cell-free fetal DNA screening detects sex chromosome aneuploidies
• Sensitivity ~90% for 45,X
• Positive result → offer diagnostic amniocentesis for karyotype confirmation

First-trimester ultrasound:

• Increased nuchal translucency (> 3.5 mm at 11-14 weeks) → consider karyotyping
• Cystic hygroma → high likelihood of Turner syndrome

Second-trimester ultrasound anomalies:

• Coarctation of aorta
• Left heart hypoplasia
• Renal anomalies
• Hydrops fetalis

Counselling: Prenatal diagnosis enables:

• Parental preparation and education
• Planned postnatal cardiac and genetic evaluation
• Informed decision-making (continuation vs termination, per parental values)

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Postnatal Case Finding

Screen for Turner syndrome if:

• Unexplained short stature (less than 3rd centile) in girls
• Delayed puberty (no breast development by age 13)
• Primary amenorrhoea (no periods by age 15)
• Neonatal lymphoedema in female infants
• Characteristic dysmorphic features (webbed neck, shield chest, cubitus valgus)
• Coarctation of aorta or left-sided cardiac anomalies

Screening test: Karyotype (30-cell analysis to exclude mosaicism)

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11. Key Guidelines

International Consensus Guidelines

Key Recommendations Summary

1. Diagnosis: Karyotype any girl with short stature, delayed puberty, or characteristic features
2. Screening at diagnosis: Echo/cardiac MRI, renal ultrasound, thyroid function, hearing assessment
3. Growth hormone: Start age 4-6 years; dose 0.045-0.05 mg/kg/day; continue until near-final height
4. Oestrogen replacement: Start age 11-12; transdermal preferred; lifelong until age ~50
5. Cardiovascular surveillance: Echo every 3-5 years; transition to cardiac MRI in adolescence; lifelong
6. Multidisciplinary care: Paediatric endocrinology lead; cardiology, audiology, psychology input
7. Transition: Structured transition to adult services age 16-18
8. Gonadectomy: If Y chromosome material present (gonadoblastoma risk)

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12. Common Exam Questions

MRCPCH Clinical Scenarios

1. "A 4-year-old girl is referred for short stature. What is your differential diagnosis and initial investigations?"

Model answer:

• Differential includes: Constitutional delay, familial short stature, Turner syndrome, growth hormone deficiency, hypothyroidism, skeletal dysplasia, chronic systemic illness
• Initial investigations: Growth chart plotting, mid-parental height calculation, bone age X-ray, karyotype (Turner syndrome), thyroid function, coeliac screen, IGF-1, full blood count, renal function
• Turner syndrome specifically considered given female sex and unexplained short stature

2. "A neonate has lymphoedema of the hands and feet. What is the most likely diagnosis and what urgent investigation is needed?"

Model answer:

• Most likely diagnosis: Turner syndrome (45,X)
• Urgent investigation: Echocardiography to exclude coarctation of the aorta (present in 10-15%)
• Also perform karyotype to confirm diagnosis
• Check femoral pulses and 4-limb blood pressures clinically

3. "What are the indications for starting growth hormone therapy in Turner syndrome?"

Model answer:

• Diagnosis of Turner syndrome is sufficient indication (no GH stimulation testing required)
• Optimal timing: Age 4-6 years
• Benefits: Increases final adult height by average 5-10 cm
• Dose: 0.045-0.05 mg/kg/day subcutaneous (higher than standard GH deficiency dosing)
• Continue until bone age ≥14 years or growth velocity less than 2 cm/year

4. "A 13-year-old girl with Turner syndrome has not started puberty. How would you manage her?"

Model answer:

• Initiate oestrogen replacement therapy
• Start low-dose transdermal oestrogen (e.g., 25 mcg estradiol patch twice weekly or 0.5 mg gel daily)
• Gradual dose escalation over 2-3 years to mimic natural puberty
• Add progesterone after 2 years or when breakthrough bleeding occurs
• Monitor Tanner staging, bone density, compliance
• Provide psychological support regarding fertility and body image

5. "What are the cardiovascular complications of Turner syndrome and how are they monitored?"

Model answer:

• Complications: Bicuspid aortic valve (30%), coarctation of aorta (10-15%), aortic root dilatation (progressive), hypertension, aortic dissection (leading cause of death)
• Monitoring:
  • Echocardiography at diagnosis, then every 3-5 years in childhood
  • Transition to cardiac MRI in adolescence/adulthood for superior aortic visualisation
  • 4-limb blood pressure at every clinic visit
  • Lifelong surveillance essential

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Viva Voce Points

Viva Point: Opening statement: "Turner syndrome is a chromosomal disorder affecting females, characterised by complete or partial absence of one X chromosome. The classic karyotype is 45,X. The cardinal triad is short stature, gonadal dysgenesis with infertility, and congenital cardiovascular anomalies, particularly left-sided obstructive lesions such as bicuspid aortic valve and coarctation of the aorta."

Key epidemiology:

• Prevalence: 1 in 2,000-2,500 live female births [2,3]
• 99% of 45,X conceptions result in spontaneous miscarriage [11]
• No association with maternal age [14]

Pathophysiology pearls:

• Short stature: SHOX gene haploinsufficiency (Xp22.33) [18]
• Ovarian failure: Accelerated oocyte apoptosis leading to streak ovaries [20]
• Cardiac anomalies: Lymphatic dysplasia affecting cardiac morphogenesis [23]

Management priorities:

1. Growth hormone: Start age 4-6 years, gain 5-10 cm final height [8,32]
2. Oestrogen replacement: Start age 11-12 years, lifelong until age ~50 [9,33]
3. Cardiovascular surveillance: Lifelong echo/MRI for aortic dissection risk [24,25]
4. Multidisciplinary input: Endocrinology, cardiology, audiology, psychology

Prognosis:

• Life expectancy reduced by ~10-13 years, primarily due to cardiovascular disease [10]
• Aortic dissection is leading cause of premature death (40× general population risk) [25]
• Quality of life generally good with appropriate support [35]

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Common Mistakes to Avoid

❌ Failing to check femoral pulses in a Turner syndrome diagnosis → miss coarctation of the aorta

❌ Ordering GH stimulation test before starting GH therapy → unnecessary; diagnosis is indication

❌ Starting oestrogen too early (before age 11) → may compromise final height

❌ Prescribing oral oestrogen as first-line → transdermal is preferred (more physiological)

❌ Forgetting lifelong cardiovascular surveillance → aortic dissection risk persists throughout life

❌ Missing Y chromosome material on karyotype → failure to perform gonadectomy → gonadoblastoma risk

❌ Assuming normal intelligence means no educational needs → specific visuospatial and maths deficits require targeted support

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13. Patient and Layperson Explanation

What is Turner Syndrome?

Turner syndrome is a condition that only affects girls. It happens when a girl is born with one X chromosome missing or incomplete. Normally, girls have two X chromosomes (XX), but girls with Turner syndrome have only one working X chromosome (or part of one is missing).

This happens by chance when the baby is developing, and it is not caused by anything the parents did or didn't do. It cannot be prevented.

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What does it mean for my daughter?

Girls with Turner syndrome are usually shorter than average and don't start puberty on their own. The main features are:

1. Short stature: Without treatment, girls with Turner syndrome are usually about 20 cm (8 inches) shorter than other girls in their family. With treatment (growth hormone injections), they can grow 5-10 cm taller.

2. Delayed puberty: The ovaries don't work properly, so girls with Turner syndrome don't start developing breasts or periods naturally. They need hormone treatment (oestrogen) as teenagers to develop normally.

3. Heart problems: Some girls (about 1 in 3) are born with heart abnormalities, particularly involving the valves or main blood vessel (aorta). These usually need monitoring throughout life, and sometimes treatment.

4. Other features: Some girls have kidney abnormalities, frequent ear infections, or learning difficulties with maths and spatial tasks. Intelligence is usually normal—most girls with Turner syndrome attend regular schools and do well.

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Can she have children?

Most women with Turner syndrome cannot have children naturally because their ovaries don't hold eggs properly. However:

• A small number (about 2-5%, usually those with mosaic Turner syndrome) can get pregnant naturally
• Many women can carry a pregnancy using donated eggs through IVF when they are older
• Adoption and choosing to be child-free are other options

If your daughter wants to have children in the future, pregnancy carries some extra risks (particularly to the heart), so careful planning with specialists is essential.

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What treatment will she need?

Growth hormone injections (ages ~4-16):

• Daily injections under the skin (like diabetes insulin)
• Helps her grow taller
• Usually started around age 4-6 and continued until she stops growing

Oestrogen hormone treatment (ages ~11-50):

• Starts around age 11-12 to help her develop breasts and start periods
• Usually given as a patch on the skin or gel
• Needs to continue lifelong (until about age 50) for bone strength and heart health

Regular check-ups:

• Heart scans (echocardiograms) to monitor the heart and aorta
• Hearing tests (ear infections are common)
• Thyroid blood tests (thyroid problems develop in about 1 in 4 girls)
• Educational support if needed

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What is the outlook?

With modern treatment, girls with Turner syndrome can expect to:

• Reach a reasonable height (usually 150-155 cm with treatment)
• Develop normally through puberty (with hormone treatment)
• Attend regular schools and go on to university/careers
• Form relationships and live independently
• Have good quality of life

The main long-term concerns are:

• Heart health: The aorta (main blood vessel) needs monitoring throughout life because there's a risk of it becoming stretched or, rarely, tearing (aortic dissection)
• Fertility: Most women cannot have biological children without egg donation
• Other health conditions: Higher risk of thyroid problems, diabetes, and hearing loss

With expert care and support, most women with Turner syndrome live full, happy, and healthy lives.

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Where can we get support?

Turner Syndrome Support Society (TSSS): UK charity providing information, support groups, and events for families affected by Turner syndrome.

• Website: tss.org.uk
• Helpline and online forums available

Clinical Genetics Services: Your local genetics centre can provide genetic counselling and information.

Specialist Turner Syndrome Clinics: Many paediatric endocrine centres run specialist Turner syndrome multidisciplinary clinics.

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14. References

Primary Sources

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2. Stochholm K, Juul S, Juel K, Naeraa RW, Gravholt CH. Prevalence, incidence, diagnostic delay, and mortality in Turner syndrome. J Clin Endocrinol Metab. 2006;91(10):3897-3902. doi:10.1210/jc.2006-0558

3. Sybert VP, McCauley E. Turner's syndrome. N Engl J Med. 2004;351(12):1227-1238. doi:10.1056/NEJMra030360

4. Turner HH. A syndrome of infantilism, congenital webbed neck, and cubitus valgus. Endocrinology. 1938;23:566-574.

5. Ford CE, Jones KW, Polani PE, de Almeida JC, Briggs JH. A sex-chromosome anomaly in a case of gonadal dysgenesis (Turner's syndrome). Lancet. 1959;1(7075):711-713. doi:10.1016/s0140-6736(59)91893-8

6. Bondy CA; Turner Syndrome Study Group. Care of girls and women with Turner syndrome: a guideline of the Turner Syndrome Study Group. J Clin Endocrinol Metab. 2007;92(1):10-25. doi:10.1210/jc.2006-1374

7. Hong D, Scaletta Kent J, Kesler S. Cognitive profile of Turner syndrome. Dev Disabil Res Rev. 2009;15(4):270-278. doi:10.1002/ddrr.79

8. Ranke MB, Saenger P. Turner's syndrome. Lancet. 2001;358(9278):309-314. doi:10.1016/S0140-6736(01)05487-3

9. Donaldson MD, Gault EJ, Tan KW, Dunger DB. Optimising management in Turner syndrome: from infancy to adult transfer. Arch Dis Child. 2006;91(6):513-520. doi:10.1136/adc.2003.035907

10. Schoemaker MJ, Swerdlow AJ, Higgins CD, Wright AF, Jacobs PA; UK Clinical Cytogenetics Group. Mortality in women with Turner syndrome in Great Britain: a national cohort study. J Clin Endocrinol Metab. 2008;93(12):4735-4742. doi:10.1210/jc.2008-1049

11. Hook EB, Warburton D. Turner syndrome revisited: review of new data supports the hypothesis that all viable 45,X cases are cryptic mosaics with a rescue cell line, implying an origin by mitotic loss. Hum Genet. 2014;133(4):417-424. doi:10.1007/s00439-014-1420-x

12. Conway GS. Turner syndrome. Medicine. 2017;45(10):611-614. doi:10.1016/j.mpmed.2017.07.008

13. Prakash S, Guo D, Maslen CL, et al. Single-nucleotide polymorphism array genotyping is equivalent to metaphase cytogenetics for diagnosis of Turner syndrome. Genet Med. 2014;16(1):53-59. doi:10.1038/gim.2013.77

14. Saenger P. Turner's syndrome. N Engl J Med. 1996;335(23):1749-1754. doi:10.1056/NEJM199612053352307

15. Wolff DJ, Van Dyke DL, Powell CM; Working Group of the ACMG Laboratory Quality Assurance Committee. Laboratory guideline for Turner syndrome. Genet Med. 2010;12(1):52-55. doi:10.1097/GIM.0b013e3181c684b2

16. Mathur A, Stekol L, Schatz D, MacLaren NK, Scott ML, Lippe B. The parental origin of the single X chromosome in Turner syndrome: lack of correlation with parental age or clinical phenotype. Am J Hum Genet. 1991;48(4):682-686.

17. Zinn AR, Ross JL. Turner syndrome and haploinsufficiency. Curr Opin Genet Dev. 1998;8(3):322-327. doi:10.1016/s0959-437x(98)80089-0

18. Rao E, Weiss B, Fukami M, et al. Pseudoautosomal deletions encompassing a novel homeobox gene cause growth failure in idiopathic short stature and Turner syndrome. Nat Genet. 1997;16(1):54-63. doi:10.1038/ng0597-54

19. Hochberg Z; 2007 Drug and Therapeutics Committee of the Lawson Wilkins Pediatric Endocrine Society. Mechanisms of steroid impairment of growth. Horm Res. 2002;58 Suppl 1:33-38. doi:10.1159/000064763

20. Modi DN, Sane S, Bhartiya D. Accelerated germ cell apoptosis in sex chromosome aneuploid fetal human gonads. Mol Hum Reprod. 2003;9(4):219-225. doi:10.1093/molehr/gag031

21. Hagen CP, Main KM, Kjaergaard S, Juul A. FSH, LH, inhibin B and estradiol levels in Turner syndrome depend on age and karyotype: longitudinal study of 70 Turner girls with or without spontaneous puberty. Hum Reprod. 2010;25(12):3134-3141. doi:10.1093/humrep/deq291

22. Mortensen KH, Andersen NH, Gravholt CH. Cardiovascular phenotype in Turner syndrome--integrating cardiology, genetics, and endocrinology. Endocr Rev. 2012;33(5):677-714. doi:10.1210/er.2011-1059

23. Gotzsche CO, Krag-Olsen B, Nielsen J, Sorensen KE, Kristensen BO. Prevalence of cardiovascular malformations and association with karyotypes in Turner's syndrome. Arch Dis Child. 1994;71(5):433-436. doi:10.1136/adc.71.5.433

24. Silberbach M, Roos-Hesselink JW, Andersen NH, et al. Cardiovascular health in Turner syndrome: a scientific statement from the American Heart Association. Circ Genom Precis Med. 2018;11(10):e000048. doi:10.1161/HCG.0000000000000048

25. Carlson M, Silberbach M. Dissection of the aorta in Turner syndrome: two cases and review of 85 cases in the literature. J Med Genet. 2007;44(12):745-749. doi:10.1136/jmg.2007.052019

26. Lippe B, Geffner ME, Dietrich RB, Boechat MI, Kangarloo H. Renal malformations in patients with Turner syndrome: imaging in 141 patients. Pediatrics. 1988;82(6):852-856.

27. Bakalov VK, Gutin L, Cheng CM, et al. Autoimmune disorders in women with Turner syndrome and women with karyotypically normal primary ovarian insufficiency. J Autoimmun. 2012;38(4):315-321. doi:10.1016/j.jaut.2012.01.015

28. Dhooge IJ, De Vel E, Verhoye C, Lemmerling M, Vinck B. Otologic disease in Turner syndrome. Otol Neurotol. 2005;26(2):145-150. doi:10.1097/00129492-200503000-00003

29. Savendahl L, Davenport ML. Delayed diagnoses of Turner's syndrome: proposed guidelines for change. J Pediatr. 2000;137(4):455-459. doi:10.1067/mpd.2000.107390

30. Ross JL, Roeltgen D, Feuillan P, Kushner H, Cutler GB Jr. Effects of estrogen on nonverbal processing speed and motor function in girls with Turner's syndrome. J Clin Endocrinol Metab. 1998;83(9):3198-3204. doi:10.1210/jcem.83.9.5087

31. Cools M, Drop SL, Wolffenbuttel KP, Oosterhuis JW, Looijenga LH. Germ cell tumors in the intersex gonad: old paths, new directions, moving frontiers. Endocr Rev. 2006;27(5):468-484. doi:10.1210/er.2006-0005

32. Baxter L, Bryant J, Cave CB, Milne R. Recombinant growth hormone for children and adolescents with Turner syndrome. Cochrane Database Syst Rev. 2007;(1):CD003887. doi:10.1002/14651858.CD003887.pub2

33. Nabhan ZM, Dimeglio LA, Qi R, Perkins SM, Eugster EA. Conjugated oral versus transdermal estrogen replacement in girls with Turner syndrome: a pilot comparative study. J Clin Endocrinol Metab. 2009;94(6):2009-2014. doi:10.1210/jc.2008-2123

34. Karnis MF, Zimon AE, Lalwani SI, Timmreck LS, Klipstein S, Reindollar RH. Risk of death in pregnancy achieved through oocyte donation in patients with Turner syndrome: a national survey. Fertil Steril. 2003;80(3):498-501. doi:10.1016/s0015-0282(03)00974-9

35. Naess EE, Bahr D, Gravholt CH. Health status in women with Turner syndrome: a questionnaire study on health status, education, and employment. Fertil Steril. 2010;94(5):1693-1697. doi:10.1016/j.fertnstert.2009.09.006

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