Patau Syndrome (Trisomy 13)
Summary
Patau syndrome is a chromosomal disorder caused by an extra copy of chromosome 13 (trisomy 13). It is the third most common autosomal trisomy after Trisomy 21 (Down syndrome) and Trisomy 18 (Edwards syndrome). Patau syndrome is characterised by severe midline defects, including holoprosencephaly (failure of the brain to divide into two hemispheres), cleft lip and palate, and cardiac malformations. Additional features include polydactyly, microphthalmia, scalp defects (cutis aplasia), and rocker-bottom feet. Prognosis is very poor, with median survival of only 7-10 days. Most affected pregnancies end in miscarriage or stillbirth. Management is palliative and supportive.
Key Facts
- Genetics: Trisomy 13 (47,XX,+13 or 47,XY,+13)
- Incidence: 1 in 10,000-20,000 live births
- Hallmark: Midline defects (holoprosencephaly, cleft lip/palate)
- Other Features: Polydactyly, Scalp defects, Microphthalmia
- Prognosis: Median survival 7-10 days; 90% die within first year
- Management: Palliative care
Clinical Pearls
"Puberty Age = 13": Mnemonic — Patau syndrome corresponds to chromosome 13.
"Midline Defects": Think Patau when you see holoprosencephaly + cleft lip/palate + cardiac defects.
"Polydactyly + Cutis Aplasia + Microphthalmia": Classic triad of external features.
"P's for Patau": Polydactyly, Palate (cleft), Patching of scalp (cutis aplasia), Pumping problems (heart defects).
Incidence
- 1 in 10,000-20,000 live births
- Higher incidence at conception (many miscarry)
Risk Factors
| Factor | Notes |
|---|---|
| Advanced maternal age | Main risk factor |
| Previous trisomy pregnancy | Slightly increased recurrence |
Genetics
- 80% full trisomy 13 (non-disjunction)
- 10% translocation (often familial)
- 10% mosaicism (may be milder)
Mechanism
- Extra copy of chromosome 13
- Leads to overexpression of genes on chromosome 13
- Results in multiple severe developmental abnormalities
Key Affected Organ Systems
- Brain: Holoprosencephaly (failure of forebrain to divide)
- Heart: VSD, ASD, PDA, dextrocardia
- Eyes: Microphthalmia, coloboma
- Hands/Feet: Polydactyly, rocker-bottom feet
- Kidneys: Polycystic kidneys, hydronephrosis
Antenatal (Ultrasound Findings)
| Finding | Notes |
|---|---|
| Holoprosencephaly | Characteristic midline brain abnormality |
| Fetal growth restriction | |
| Cleft lip/palate | Often central/bilateral |
| Cardiac defects | Complex |
| Polydactyly | Extra digits (especially postaxial) |
| Rocker-bottom feet | |
| Omphalocele | Abdominal wall defect |
Postnatal Features
| System | Features |
|---|---|
| CNS | Holoprosencephaly, Microcephaly, Severe intellectual disability |
| Craniofacial | Cleft lip/palate, Microphthalmia, Low-set ears, Sloping forehead |
| Scalp | Cutis aplasia (missing areas of skin) |
| Cardiac | VSD, ASD, PDA, Coarctation |
| Limbs | Postaxial polydactyly, Rocker-bottom feet, Clenched fists |
| Renal | Polycystic kidneys |
| GI | Omphalocele |
General
- Severe dysmorphic features
- Microcephaly
- Hypotonia or hypertonia
- Apnoeic episodes
Specific
- Cleft lip/palate (often midline or bilateral)
- Scalp defects (cutis aplasia)
- Small, close-set or absent eyes (microphthalmia, anophthalmia)
- Extra digits (polydactyly)
- Cardiac murmur
Prenatal
| Test | Notes |
|---|---|
| Combined test (1st trimester screening) | Raised risk leads to diagnostic testing |
| NIPT | Non-invasive screening (cfDNA) |
| Amniocentesis / CVS | Karyotype confirms diagnosis |
| Fetal ultrasound | Identifies structural anomalies |
Postnatal
| Test | Purpose |
|---|---|
| Karyotype | Confirms trisomy 13 |
| Echocardiogram | Cardiac defects |
| Renal ultrasound | Renal anomalies |
| MRI brain | Holoprosencephaly, other CNS defects |
Antenatal Counselling
- Detailed discussion about prognosis
- Options: Continue pregnancy with palliative approach, or termination
- Support from genetic counsellor, specialist midwife
Postnatal Management
┌──────────────────────────────────────────────────────────┐
│ PATAU SYNDROME MANAGEMENT │
├──────────────────────────────────────────────────────────┤
│ │
│ SUPPORTIVE/PALLIATIVE CARE: │
│ • Comfort-focused care │
│ • Warmth, feeding support, symptom control │
│ • Family support and bereavement care │
│ │
│ DECISION-MAKING: │
│ • Discussions about DNACPR / limitations of treatment │
│ • Individualised approach (some families may opt for │
│ limited interventions, e.g., corrective surgery) │
│ │
│ INTERVENTIONS (If family chooses): │
│ • Some centres may offer palliative surgery for comfort │
│ • Rarely, cardiac or other surgery in mosaics │
│ │
│ FAMILY SUPPORT: │
│ • SOFT (Support Organisation for Trisomy) │
│ • Memory making (photos, handprints) │
│ • Sibling support │
│ │
└──────────────────────────────────────────────────────────┘
Fatal
- Cardiopulmonary failure (most common cause of death)
- Apnoea
- Sepsis
If Survive
- Profound intellectual disability
- Seizures
- Feeding difficulties
- Visual and hearing impairment
Survival
| Timepoint | Survival |
|---|---|
| 1 week | ~50% |
| 1 month | ~30% |
| 1 year | ~10% |
Long-Term Survivors
- Very rare
- Usually mosaicism
- Severe disability
Key Guidelines
- SOFT: Support Organisation for Trisomy 13, 18 and Related Disorders
Key Evidence
Prognosis
- Median survival 7-10 days
- Long-term survival rare
What is Patau Syndrome?
Patau syndrome happens when a baby has an extra copy of chromosome 13. It causes severe problems with how the baby develops before birth.
What Are the Signs?
- Problems with the brain developing properly
- Cleft lip and/or palate
- Extra fingers or toes
- Small eyes or no eyes
- Heart defects
- Patches of missing skin on the scalp
What is the Outlook?
Sadly, Patau syndrome is a very serious condition. Most babies with this condition do not survive beyond the first few weeks of life. Very few live beyond one year.
How is it Managed?
Care focuses on keeping the baby comfortable and supporting the family. Some families may choose comfort-focused care only, while others may opt for some treatments.
Support
Organisations like SOFT (Support Organisation for Trisomy 13, 18 and Related Disorders) offer support and information for affected families.
Primary Resources
- SOFT (Support Organisation for Trisomy 13, 18 and Related Disorders). soft.org.uk
Key Studies
- Carey JC. Trisomy 18 and trisomy 13 syndromes. In: Cassidy SB, Allanson JE, eds. Management of Genetic Syndromes. 3rd ed. Wiley-Blackwell; 2010.