Patau’s syndrome (Trisomy 13): a serious but rare genetic disorder

Posted: 10/11/2020

Patau’s syndrome – otherwise known as ‘Trisomy 13’ – is a chromosomal condition associated with severe intellectual disability and physical abnormalities in many parts of the body. Common features of this condition include: heart defects; brain or spinal cord abnormalities; extra fingers or toes (polydactyl); weak muscle tone (hypotonia); very small or poorly developed eyes (microphthalmia); renal abnormalities; and a cleft lip and cleft palate. Most infants born with this condition survive days or weeks: only 5-10% live past their first year.

Approximately 1 in 16,000 infants are born with Trisomy 13 – so called because it results from having three copies of chromosome 13 in each cell rather than the usual two. The risks of having an infant with Trisomy 13 increase with the age of the mother, as is the case with Down’s syndrome (Trisomy 21) and Edward’s syndrome (Trisomy 18).

Several antenatal screening tests are available to test for Patau’s syndrome. One of them, the ‘combined test’, can be performed only between around 11 and 14 weeks into the pregnancy. If the test produces a ‘higher risk’ result (defined as a 1 in 150 chance of the fetus being affected), the mother is offered more invasive testing of the amniotic fluid (amniocentesis), placental tissue (CVS) or fetal blood (fetal blood sampling). Each of these tests, however, carries a small but significant risk of miscarriage.

On occasion, features indicative of Patau’s syndrome may be picked up on the ‘anomaly’ ultrasound scan performed at 20 weeks of pregnancy, even if the mother has been classed as ‘lower risk’ on combined screening.

The clinical negligence team at Penningtons Manches Cooper is currently investigating a case involving alleged failures to diagnose Patau’s syndrome by initially offering combined screening within the appropriate window of opportunity, and subsequently to pick up on fetal abnormalities evident later on in the pregnancy. The team has obtained supportive expert evidence from a fetal medicine expert and will be inviting the defendant to make an early admission of liability.

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