Patau syndrome (Trisomy 13) — causes, features, diagnosis, and care

Genetics and causes

The underlying problem is chromosomal. In most cases an error in cell division produces an extra chromosome 13 in every cell, a process that commonly results from nondisjunction during meiosis. Less commonly, a Robertsonian translocation — a specific rearrangement between chromosomes — can produce a balanced carrier parent and increase recurrence risk. Mosaic Trisomy 13, where only a proportion of cells carry the extra chromosome, causes a more variable and sometimes milder presentation.

Typical clinical features

Findings vary, but common features at birth include structural brain anomalies (for example, holoprosencephaly), facial differences such as cleft lip or palate, small or malformed eyes (microphthalmia), extra fingers or toes (polydactyly), scalp defects (cutis aplasia), and severe congenital heart defects (ventricular septal defects, atrial septal defects). Growth restriction, profound intellectual disability and problems with feeding and breathing are frequent.

• Central nervous system: holoprosencephaly, seizures
• Craniofacial: cleft lip/palate, microphthalmia
• Limbs and skin: polydactyly, scalp defects
• Cardiac and visceral: complex heart defects, renal anomalies

Diagnosis and prenatal testing

Chromosomal anomalies can be suspected on prenatal ultrasound or screening tests and confirmed by diagnostic procedures. Noninvasive screening methods include maternal serum screening and cell-free fetal DNA in maternal blood; detailed ultrasound may identify structural markers. Definitive diagnosis uses invasive testing such as chorionic villus sampling or amniocentesis with karyotype or chromosomal microarray analysis. After birth, a blood karyotype or genetic testing establishes the diagnosis.

Prognosis and management

Prognosis is guarded: many affected fetuses result in miscarriage or stillbirth, and neonatal mortality is high. Infants who survive the newborn period often have severe disability and require ongoing medical, surgical and supportive care. Management focuses on treating specific anomalies (for example cardiac surgery when feasible), preventing complications, and providing nutritional, respiratory and palliative support. Decisions about interventions are individualized and often made by families with multidisciplinary clinical teams.

Epidemiology, counseling and notable distinctions

Patau syndrome is one of the autosomal trisomies encountered in clinical genetics and is the rarest of the three well-known full trisomies in live births; trisomy conditions such as Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18) occur more frequently. Risk increases with advancing maternal age. Genetic counseling is recommended for affected families: karyotyping can identify translocation carriers and provide individualized recurrence risk estimates, while supportive resources and early planning help address medical and ethical decisions.

For clinicians and families, clear communication about likely outcomes, available interventions and supportive care options is essential. Long-term follow-up is coordinated among pediatrics, cardiology, neurology, surgery, genetics and palliative care teams to optimize quality of life for affected infants and children.