Patau syndrome (also known as trisomy 13) is considered the 3^rd commonest autosomal trisomy.

Patau syndrome, Down syndrome (trisomy 21), and Edwards syndrome (trisomy 18) are the only three trisomies compatible with extrauterine life. However, few infants with either Patau or Edwards syndrome live more than a few days after birth.

Epidemiology

The estimated incidence is approximately 1:6000. There may be an increased incidence with advanced maternal age.

Associations

• single umbilical artery

Clinical presentation

Described features are protean and include:

• congenital heart disease: 50-80%

  • hypoplastic left heart syndrome (HLHS)

  • ventricular septal defect (VSD)

• central nervous system/head and neck abnormalities: 70%

  • holoprosencephaly: most well-known associated CNS anomaly: ~40-50% ⁹

  • microcephaly

  • fetal hydrocephalus

  • enlarged cisterna magna

  • agenesis of the corpus callosum

  • persistent stapedial artery ⁵

  • retinal dysplasia ³ 

• spinal anomalies

  • spina bifida

• intrauterine growth restriction (IUGR): tends to be early

• abnormal facies: 90%, strong marker

  • cleft lip +/- palate: ~45% ⁹

  • microphthalmia: rarely anophthalmia ¹⁰

  • micrognathia ⁶

  • hypotelorism

  • hypertelorism

  • cyclopia

  • proboscis

• skeletal abnormalities

  • polydactyly: 70% (tends to be post-axial)

  • rocker bottom feet

  • clenched hands +/- overlapping digits

• abdominal wall abnormalities

  • bladder exstrophy

  • omphalocele

• genitourinary anomalies

  • cryptorchidism

  • cystic renal dysplasia

Pathology

Three forms are known 

• free trisomy 13: classical form

• translocation trisomy 13

• mosaic trisomy 13

Markers

• reduced maternal serum alpha fetoprotein (MSAFP)

• reduced maternal beta HCG

• reduced PAPP-A

Radiographic features

Ultrasound

Many of the individual clinical features listed above may be seen on ultrasound. Other general features include:

• abnormal liquor volumes: either polyhydramnios (more common) or oligohydramnios

• evidence of intrauterine growth restriction (IUGR): especially early

• increased nuchal thickness

• evidence of hydrops fetalis

• echogenic bowel ⁶

• echogenic chordae tendineae ⁷

Treatment and prognosis

The syndrome carries a poor prognosis, with most cases ending in fetal demise or neonatal death. Management is mainly supportive.

Differential diagnosis

Individuals with Meckel-Gruber syndrome may exhibit some clinical features similar to that of trisomy 13.