Trisomy 13 syndrome (Patau syndrome) is a disorder of human chromosomes which occurs in approximately 1 in 10,000-25,000 live-born infants. Trisomy refers to three copies of a chromosome instead of the normal two and in Trisomy 13 there is the presence of an extra #13 chromosome. Trisomy 13 Syndrome is a rare chromosomal disorder in which all or a portion of chromosome 13 appears three times (trisomy) rather than twice in cells of the body. Patau syndrome is the most lethal of all the viable trisomies, with most resulting in spontaneous
Like all nondisjunction conditions (such as Down syndrome and Edwards syndrome), the risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average. In other words, she has three copies of her chromosome 13 when she should have just two. Brain anomalies in 9 cases of cytogenetically proven 18 trisomy were reported. Individuals with trisomy 13 often have heart defects, brain or spinal cord abnormalities, very small or poorly developed eyes (microphthalmia), extra fingers or toes, an opening in the lip (a cleft lip) with or without an opening in the roof of the mouth (a cleft palate), and weak muscle tone (hypotonia). In some affected individuals, only a percentage of cells may contain the extra 13th chromosome (mosaicism), whereas other cells contain the normal chromosomal pair. Trisomy 13 is a genetic disorder that your baby gets when she has an extra 13th chromosome. Trisomy 13, or Patau syndrome, is a rare chromosomal anomaly with an incidence of approximately 1 in 5000 to 1 in 20,000 live births.1,2It is the third most common autosomal triploidy in liveborn infants, after trisomy 21 and 18. Full trisomy 13 is caused by nondisjunction of chromosomes during meiosis (the mosaic form is caused by nondisjunction during mitosis). In some affected people, only a portion of cells contains the extra chromosome 13 (called mosaic trisomy 13), whereas other cells contain the normal chromosome pair. Trisomy 13 is a type of chromosome disorder characterized by having 3 copies of chromosome 13 in cells of the body, instead of the usual 2 copies.