Trisomy 13 (Patau Syndrome)

Definition

Epidemiology

• Occurs in about 1/10,000 live births
• Highest rate of death in utero of the three most common trisomies (21 and 18)

Clinical Features

• Low birth weight
• Microphthalmia
• Hypotelorism
• Cleft lip and palate  ~60-80%
• Low set ears
• Scalp skin defects (cutis aplasia)
• Holoprosencephaly
• Sloping forehead
• Microcephaly
• Capillary Hemangiomas
• Congenital heart defects (VSD, PDA, ASD) ~ 80%
• Overlapping fingers and toes
• Polydactyly
• Hypoplastic nails
• Rocker-bottom feet
• Renal abnormalities
• GI abnormalities

Diagnosis

This syndrome can be confused with Meckel-Gruber syndrome (autosomal recessive).  Tri 13 involves holoprosencephaly, postaxial polydactyly, and renal anomalies; often an encephalocele is present.  In MG, however, there is cystic dysplasia of the kidneys, fibrosis of the liver and sometimes hydrocephalus.  Renal ultrasound and chromosomal analysis allow differentiation of the two syndromes.

Prognosis

Most die within the neonatal period and even before diagnosis is made.  Those who survive are often mosaics, but they have severe mental and physical developmental impairment.