Trisomy 13 (Patau Syndrome) Characteristics

Questions and Answers

What is the primary mechanism responsible for the development of Trisomy 13?

Meiotic nondisjunction

What is the characteristic facial anomaly often seen in Trisomy 13?

Low-set, malformed ears

What is the most common congenital heart defect seen in Trisomy 13?

Ventricular septal defect

What is the incidence of Trisomy 13 in live births?

1:7,400 Signup and view all the answers

What is the typical prognosis for infants with Trisomy 13?

Only approximately 11% of infants survive past 12 months of age Signup and view all the answers

What is the term for the congenital absence of skin, often seen in Trisomy 13?

Aplasia cutis congenita Signup and view all the answers

What is the term for the small orbits, which may be unilateral or bilateral, seen in Trisomy 13?

Microphthalmia Signup and view all the answers

What is the first trimester screening test used to detect Trisomy 13?

Ultrasound and maternal serum testing Signup and view all the answers

Study Notes

Trisomy 13 (Patau Syndrome)

Karyotype

Female: 47,XX,+13
Male: 47,XY,+13

Incidence

Approximately 1 in 7,400 live births

Pathogenesis

Meiotic nondisjunction
Abnormal fusion of prechordal mesoderm leading to midline defects

Clinical Features

Craniofacial Anomalies

Microcephaly
Holoprosencephaly
Characteristic facial anomalies
Cleft lip and palate
Low-set, malformed ears
Bulbous nose
Small chin

Ocular Anomalies

Microphthalmia (small orbits) - unilateral or bilateral
Coloboma
Ocular hypotelorism

Limb Anomalies

Polydactyly (primarily hexadactyly)
Flexed fingers

Cardiovascular Anomalies

Congenital heart defects
Ventricular septal defect
Patent ductus arteriosis

Skin Anomalies

Aplasia cutis congenita: congenital absence of skin (scalp lesions with a punched-out appearance)
Capillary hemangioma

Other Anomalies

Rocker-bottom feet
Omphalocele
Visceral and genital anomalies (e.g., polycystic kidney disease)

Diagnostics

Detected during first trimester screening with combined ultrasound and maternal serum testing
Decreased PAPP-A, increased nuchal translucency

Prognosis

Infants usually die before the age of 1
Only approximately 11% of infants survive past 12 months of age

Mnemonic

7 Ps of Patau syndrome: holoprosencephaly, cleft lip and palate, polydactyly, pump disease (congenital heart disease), polycystic kidney disease, cutis aplasia