By skyforbes 
What are the symptoms of trisomy 13 (Patau syndrome)?
Symptoms of trisomy 13 affect several different parts of the body and range in severity for each person diagnosed with the condition. Symptoms of trisomy 13 include:
- Heart abnormalities present at birth (congenital).
- Physical growth irregularities with many cases targeting the spinal cord.
- Severe issues with cognitive function.
- Underdeveloped internal organs.
Physical symptoms
Physical symptoms of trisomy 13 include:
- Cleft lip or cleft palate.
- Difficulty gaining weight.
- Extra fingers or toes (polydactyly).
- Ears forming low on the head.
- Growth abnormalities in the arms and legs.
- Low muscle tone (hypotonia).
- Small head and lower jaw.
- Very small, close together or underdeveloped eyes.
Internal organ symptoms
Symptoms of trisomy 13 that affect the development of internal organs include:
- Gastrointestinal (GI) problems that make eating difficult.
- Heart failure.
- Hearing problems.
- Underdeveloped lungs.
- Vision problems.
Since internal organ symptoms can be life-threatening, nearly 80% of babies diagnosed with Trisomy 13 don’t survive past their first year. Those that do survive may face more life-threatening complications after their first year including an increased risk of developing cancer and seizures.
What causes trisomy 13 (Patau syndrome)?
A third chromosome 13 that attaches to a pair of chromosomes causes trisomy 13. A person with trisomy 13 has 47 total chromosomes.
There are normally 46 chromosomes in your body. Chromosomes carry DNA in cells, which works as an instruction manual to tell your body how to form and function. Genes are segments of your DNA that are chapters in your body’s instruction manual.
Cells initially form in reproductive organs by dividing from one fertilized cell, which is a combination of the sperm and the egg. The newer cells divide and copy themselves with half the amount of DNA as the original cell. During this process of cell division, a trisomy (when a third chromosome joins a pair) can occur randomly as cells re-type the instruction manual word for word. Any time that there’s a typo, symptoms of trisomy 13 occur because your cells don’t have the instructions they need to form and function properly.
There are three possible ways for a trisomy to form at chromosome 13 depending on how the chromosomes come together.
Complete trisomy 13
Random copying errors where more genetic material connects to a chromosome than necessary (complete trisomy 13) during the formation of the sperm and egg before conception causes trisomy 13. People with trisomy 13 have three copies of chromosome 13 instead of two. The extra genetic material attached to chromosome 13 causes symptoms of the condition.
Translocation
In about 20% of trisomy 13 cases, symptoms occur when part of chromosome 13 attaches to a nearby chromosome when eggs and sperm form (translocation) during fetal development. In this case, there are two pairs of chromosome 13, and an additional copy of chromosome 13 forms and bonds with a nearby chromosome pair, not necessarily in the 13th position.
Mosaic trisomy 13
In rare cases, an extra copy of chromosome 13 appears in some cells in the body but not all cells. This means that some cells in the body have three chromosome 13’s and others only have a pair of chromosome 13 (euploid). The severity of symptoms for a mosaic trisomy 13 diagnosis depends on how many cells have the third copy of trisomy 13. Symptoms are more severe if more cells have a third copy.