Trisomy 13 syndrome is a rare genetic disorder where an individual has three copies of chromosome 13 material instead of two copies, according to MedlinePlus. This extra material is occasionally attached to another chromosome.
Infants and children with trisomy 13 syndrome may have a wide range of symptoms, explains WebMD. Symptoms include cleft lip, cleft palate, severe mental retardation, developmental delays and abnormally small eyes. Affected children may have extra fingers and toes, and males may have undescended testes.
Trisomy 13 syndrome causes various head and facial malformations such as malformed, low-set ears, widely set eyes, scalp defects, a sloping forehead and a broad, flat nose, according to WebMD. Symptoms can also include kidney malformations, structural congenital heart defects, incomplete brain development, failure to thrive and apnea. Affected children may also have decreased muscle tone and a lot of difficulty with feeding.
Trisomy 13 syndrome occurs in approximately 1 in every 10,000 newborns, explains MedlinePlus. This syndrome generally develops due to conditions within the sperm or the egg rather than through being passed down through families. Complications develop immediately, and over 90 percent of children with trisomy 13 syndrome die within the first year. There are variations of this syndrome, including trisomy 13 mosaicism and partial trisomy.