Patau syndrome, also called trisomy 13, is the least common and most severe of the viable autosomal trisomies. Median survival is fewer than 3 days. First identified as a cytogenetic syndrome in 1960, Patau syndrome is caused by an extra copy of chromosome 13, a medium-length acrocentric chromosome. Cytogenetic analysis is a necessary step in the prenatal diagnosis of Patau syndrome. Referral to a geneticist or genetic counselor is important for appropriate counseling regarding recurrence ... Trisomy 13 also known as Patau syndrome occurs due to the numerical chromosomal abnormality in which an extra copy of chromosome 13 present with a pair. Trisomy 13, or Patau syndrome, is a genetic disorder that affects the development of a baby. Learn about the symptoms, diagnosis, and treatment options. Patau's syndrome is a rare genetic disorder caused by having an extra copy of chromosome 13. It affects about 1 in 4,000 births and causes severe developmental problems and often death. Learn about the symptoms, causes, screening and treatment options.