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Patau syndrome (chromosome 13 trisomy syndrome)
Medical expert of the article
Last reviewed: 12.07.2025
Patau syndrome (trisomy 13) occurs when there is an extra chromosome 13 and includes malformations of the forebrain, face, and eyes; severe mental retardation; and low birth weight.
Patau syndrome (trisomy 13) occurs in about 1/10,000 live births; about 80% have complete trisomy 13. The likelihood of having a child with Patau syndrome increases with maternal age, and the extra chromosome is usually inherited from the mother.
What causes Patau syndrome?
Children with the syndrome are more often born to women over 35 years of age. The probability of having a child with trisomy 13 again in families does not exceed 1% and is not a contraindication for repeated childbearing.
Symptoms of Patau syndrome
Children are born small for their gestational age. Midline abnormalities (eg, scalp defects, cutaneous sinus defects) are common. Holoprosencephaly (abnormal division of the forebrain) is common. Associated facial abnormalities often include cleft lip and palate. Microphthalmia, colobomas (clefts of the iris), and retinal dysplasia are also common. The supraorbital margins are not prominent, and the palpebral fissures are often narrow. The auricles are malformed and usually low-set. Deafness is common. Loose folds of skin are often located on the back of the neck. Simian crease (a single transverse groove on the palm), polydactyly, and excessively convex narrow nails are also common. Severe congenital malformations of the cardiovascular system occur in about 80% of cases; dextrocardia is common. Genital anomalies are common in both boys and girls; boys have cryptorchidism and scrotal anomalies, and girls have a bicornuate uterus. Episodes of apnea are common in the first months of life. Severe mental retardation is common.
Patau syndrome is characterized by congenital eye defects (coloboma of the iris, microphthalmos, and anophthalmos), cleft lip and/or palate, aplasia of the scalp, postaxial polydactyly, congenital heart defects, and holoprosencephaly. Multiple congenital brain defects and profound mental retardation are typical. High mortality - no more than 10% of children survive to 1 year.
Diagnosis of Patau syndrome
The diagnosis can be suggested prenatally by abnormalities in the ultrasound examination of the fetus (for example, intrauterine growth retardation) or the results of a screening examination of the mother, and after the birth of the child by its characteristic appearance.
Confirmation in both cases is carried out by examining the karyotype.
[ What tests are needed?
Who to contact?
What is the prognosis for Patau syndrome?
Most patients (80%) with Patau syndrome have such severe developmental defects that they die in the first month of life; less than 10% survive more than one year.