Patau syndrome, also known as trisomy 13 and trisomy D, is a chromosomal abnormality, a syndrome in which a patient has an additional chromosome 13 due to a nondisjunction of chromosomes during meiosis.
Causes
Trisomy 13 occurs when extra DNA from chromosome 13 appears in some or all of the body’s cells.
- Trisomy 13 — the presence of an extra (third) chromosome 13 in all of the cells.
- Trisomy 13 mosaicism — the presence of an extra chromosome 13 in some of the cells.
- Partial trisomy — the presence of a part of an extra chromosome 13 in the cells.
Incidence
Patau syndrome is the least common and most severe of the viable autosomal trisomies.
Trisomy 13 occurs in about 1 out of every 10,000 newborns.
Median survival is fewer than 3 days, with only one in 20 children surviving longer than 6 months.
The sex ratio at birth is slightly skewed toward females, presumably because of decreased survival among males.
Clinical Presentation
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Newborns with Patau syndrome typically present in the neonatal period with low Apgar scores and may have the following conditions:
- Cleft lip
- Cleft palate
- Polydactyly (postaxial)
- Microcephaly
- Rocker-bottom feet
- Microphthalmia Continue reading »

