Trisomy 13 (Patau Syndrome): Signs and Symptoms
Trisomy 13 presents with a characteristic triad of craniofacial, cardiac, and limb abnormalities, including microphthalmia/anophthalmia, cleft lip and palate, polydactyly, and severe congenital heart defects, with most affected infants dying within the first year of life. 1, 2, 3
Craniofacial Features
The most recognizable facial abnormalities include:
- Cleft lip and palate - present in the majority of cases and often bilateral 1, 2, 4
- Microphthalmia or anophthalmia (small or absent eyes) - part of the classic clinical triad 2, 4
- Microcephaly with sloping forehead - characteristic head shape abnormality 2
- Low-set ears with abnormal ear structure 2
- Short neck 2
These dysmorphic features are typically evident at birth and aid in clinical diagnosis even before chromosomal confirmation 1, 2.
Cardiac Abnormalities
Congenital heart defects occur in up to 80% of patients and are a major cause of early mortality:
- Ventricular septal defect (VSD) - most common cardiac lesion 1
- Atrial septal defect (ASD) 1
- Patent ductus arteriosus (PDA) 1
- Non-cyanotic heart defects are more common than cyanotic lesions 4
A pansystolic murmur at the left sternal border is frequently detected on initial examination 1. Cardiac complications are well-described and contribute significantly to the high mortality rate 3.
Limb and Skeletal Abnormalities
- Polydactyly (extra fingers or toes) - part of the classic triad 2, 4
- Congenital clubfoot 1
- Orthopedic complications requiring monitoring 3
Central Nervous System Defects
- Holoprosencephaly - though less frequent than historically reported, remains a serious finding 4
- Neurological complications affecting quality of life 3
- Severe intellectual disabilities in survivors 5
Abdominal and Genitourinary Abnormalities
- Omphalocele (abdominal wall defect) - occurs less frequently than previously stated in literature 4
- Polycystic kidney disease 4
- Genitourinary complications requiring surveillance 3
- Single umbilical artery - though less common than expected 4
Other Systemic Manifestations
- Respiratory complications - significant contributor to morbidity 3
- Otolaryngologic issues 3
- Abdominal complications 3
Prognosis and Survival
- Mortality rate of 85-90% within the first year of life, with most deaths occurring before 6 months 1, 3
- Median survival of approximately 95 days in recent series 4
- Only 5-10% survive beyond the first year, with mosaic or partial trisomy 13 having better prognosis than full trisomy 6
- The longest documented survivor of non-mosaic trisomy 13 reached 84 months 4
Clinical Variability and Mosaicism
Important caveat: Variable expressivity exists even in non-mosaic cases, not solely related to chromosomal mosaicism 4. Patients with mosaic trisomy 13 demonstrate different clinical spectra and improved survival compared to full trisomy 5, 4. The severity of associated anomalies—particularly absence of holoprosencephaly, omphalocele, and severe renal disease—correlates with longer survival 4.
Prenatal Detection
- Low hCG levels (approximately 0.62 multiples of median) on maternal serum screening, opposite to the elevated pattern seen in Down syndrome 7
- Prenatal ultrasound may detect major structural anomalies, though certain serious defects occur less frequently than expected 4
- Diagnostic confirmation requires chromosomal analysis via CVS or amniocentesis 8