Patau syndrome – Trisomy 13

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
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
• Scalp defects (cutis aplasia)
• Omphalocele
• Hernias
• Neural tube defects
• Stillbirth and in utero fetal demise are common pregnancy outcomes
• Cardiac defects occur in 80% of cases
• Holoprosencephaly, in which the brain does not divide completely into halves, is often present and is generally signaled by the presence of midline facial defects. Facial defects include the following:
• Hypotelorism
• Microphthalmia
• Anophthalmia
• Absent or malformed nose or proboscis
• Severe clefting of the lip and/or palate.

Management
Medical management of children with Trisomy 13 is planned on a case-by-case basis and depends on the individual circumstances of the patient. Treatment of Patau syndrome focuses on the particular physical problems with which each child is born. Many infants have difficulty surviving the first few days or weeks due to severe neurological problems or complex heart defects. Surgery may be necessary to repair heart defects or cleft lip and cleft palate. Physical, occupational, and speech therapy will help individuals with Patau syndrome reach their full developmental potential.

Recurrence
Unless one of the parents is a carrier of a translocation the chances of a couple having another trisomy 13 affected child is less than 1% (less than that of Down Syndrome).