Patau syndrome, or Trisomy 13 and Trisomy D, is a rare syndrome in which a patient has an extra chromosome 13. The additional copy of chromosome 13 in Patau syndrome interferes with the normal course of development, causing chronic neurological, heart and kidney defects. Similar to the other nondisjunction conditions – Down syndrome and Edwards syndrome – the risk of this syndrome is associated with the increased maternal age at pregnancy. Patau syndrome affects roughly one in 10,000 live births, equally affecting people of all ethnic backgrounds.

Most of the time, Patau syndrome results from trisomy 13, meaning that every cell in the body contains three copies of chromosome 13 instead of two copies. In some rare cases, it occurs when just a few of the body’s cell have an additional copy, leading to a mixed population of cells with a differing number of chromosomes, known as mosaic Patau.

Patau syndrome might also occur when part of chromosome 13 attaches to another chromosome prior or at conception. These individuals have two copies of chromosome 13, plus additional material from chromosome 13 linked to another chromosome.

Patau syndrome is usually not inherited, they occur as random events throughout the formation of reproductive cells, both eggs and sperm. An error known as non-disjunction might result in reproductive cells with an atypical number of chromosomes. Mosaic Patau syndrome is not inherited either, as it takes place as a random error during cell division in the stage of fetal development.

However, Patau syndrome might be inherited due to a translocation, meaning an unaffected individual might carry a repositioned genetic material between chromosome 13 and another chromosome. The repositioning is called balanced translocation as there is no additional material from chromosome 13. Despite the fact that these people do not present any signs of Patau syndrome, have high chances of having children with this syndrome.

Newborns with Patau syndrome that survive to gestation and birth share common abnormalities, such as extra fingers or toes, deformed feet – also known as rocker-bottom feet, various neurological problems including small head – microcephaly, failure of the forebrain to properly split during gestation, chronic deficiency, different facial defects including small eyes, malformed nose, cleft lip or cleft palate, heart and kidney defects or abnormal genitalia.

The signs of Patau syndrome are obvious at birth, but it might be mistaken for Edwards syndrome, reason why genetic testing should be carried out to confirm the diagnosis. Additionally, computed tomography – CT or magnetic resonance imaging – MRI should be performed to check for heart, kidney and brain defects. An echocardiogram should also be carried out because of the common heart defects associated with Patau syndrome.

Trisomy 13 was initially observed by Erasmus Bartholin in 1657, but the chromosomal nature of the syndrome was determined in 1960 by Dr. Klaus Patau and the disease is named in his honor.

The treatment of children with trisomy 13 is carried out on a case-by-case basic and depends on the specific circumstances of the patient. The treatment concentrates on the particular physical problems each infant is born. Several infants face problems in surviving the first days or weeks because of the numerous neurological problems or multiple heart effects. Surgical procedure might be necessary to fix heart defects or cleft lip and/or cleft palate. Different and combined – physical, occupational and speech – therapy will help individuals suffering from Patau syndrome to reach their complete developmental potential.