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  • A 38-year-old woman is 12 weeks pregnant. She has had an uncomplicated course so far, and presents to her obstetrician for first trimester screening. She undergoes fetal ultrasound which is inconclusive. Serum labs show decreased β-HCG and decreased PAPP-A. After thorough discussion with her obstetrician, she decides to forgo any invasive testing and opted for a 2nd trimester screening via serum testing. At that time, lab results are normal. A repeat fetal ultrasound shows cerebral malformations.
  • Overview
    • Patau syndrome is an autosomal trisomy disorder of chromosome 13 characterized by severe intellectual disability and characteristic facial features, including cleft lip/palate, microcephaly, and microphthalmia
  • Epidemiology
    • incidence
      • 1 in 8,000-15,000
      • rarest and most severe of the autosomal trisomies
    • risk factors
      • increased maternal age
  • Genetics 
    • trisomy of chromosome 13
    • more rarely due to partial trisomy of chromosome 13 or translocation
  • Associated conditions
    • polycystic kidney disease
    • congenital heart disease
  • Prognosis
    • many instances of Patau syndrome result in fetal demise
    • patients die by age 1 with median survival of 3 days
    • there are reports of children surviving into teenage years
    • most common cause of death is cardiopulmonary arrest
  • Symptoms
    • severe intellectual disability
    • holoprosencephaly  
      • brain malformation associated with severe neurological dysfunction
      • brain does not divide into halves
    • cardiac anomalies
      • patent ductus arteriosus and septal wall defects are common
  • Physical exam
    • inspection
      • cleft lip or cleft palate
      • cutis aplasia on the scalp
      • rocker-bottom feet
      • polydactyly
      • omphalocele
      • hernias
      • neural tube defects
  • Fetal ultrasound
    • indication
      • abnormal aneuploidy screening or on routine ultrasonography
    • findings
      • growth restriction
      • craniofacial defects and cerebral malformations
      • cardiac anomalies
  • Genetic testing
    • prenatal aneuploidy screening and/or prenatal ultrasound can often screen for Patau syndrome
      • confirm with prenatal amniocentesis (15 weeks+ gestation) or chorionic villus sampling (10-12 weeks gestation)
      • cytogenetic testing or fluorescent in-situ hybridization (FISH)
Viable Autosomal Trisomies

Trisomy 13
Trisomy 18
Trisomy 21
  • Trisomy 13 is the least common viable trisomy
  • It is also the most severe
  • Trisomy 18 is the 2nd most common viable trisomy
  • Trisomy 21 is the most common viable trisomy
  • Death by age 1
  • Death by age 1
  • Normal prognosis
First trimester serum markers
  • β-HCG
  • PAPP-A
  • β-HCG
  • PAPP-A
  • β-HCG
  • PAPP-A
Second trimester serum markers
  • Normal
  • Alpha fetoprotein
  • β-HCG
  • Estriol
  • Normal/↓ inhibin A
  • Alpha fetoprotein
  • β-HCG
  • Estriol
  • Inhibin A
  • Management approach
    • there is no cure
    • surgical options are typically deferred for the first few months of life as there is a high risk of mortality in that period
  • Surgical
    • surgical correction of anomalies
      • indications
        • highly dependent on infant’s survival and specific anomalies
  • Death
  • Infections

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