12th April 2024

Down syndrome

Down syndrome is a well-known and recognised genetically acquired condition. This is a result of the presence of an extra chromosome at Ch21, which resulted from either the failure to separate (most common), Robertsonian translocation or mosaicism (rare). The risk of Down’s increases with maternal age, with a risk of 1:800 at the age of 30 increasing significantly to 1:100 by 40.

People with Down’s have certain facial features such as almond-shaped eyes slanting upwards, flat face, protruding tongue and small ears. Due to anatomical variation, they are at an increased risk of developing otitis media, eardrum perforation and hearing loss. Down’s patients are predisposed to developing a wide variety of conditions including cardiac abnormalities (atrioventricular septal defect (most common), ventricular septal defect (2nd), atrial defect, tetralogy of Fallot, PDA), GI abnormalities (Hirschsprung disease, duodenal atresia, bowel stenosis, imperforate anus, Coeliac’s disease) and neurological abnormalities (hypotonia, seizures, early onset dementia, learning difficulties). As well as this. There is an increased risk of leukaemia and hypothyroidism.

Investigations

The likelihood of a neonate having Down syndrome can be identified through one of two national screening tools: the combined test and the quadruple test. If the risk is sufficient, diagnosis can be made via amniocentesis or chorionic villus sampling.

Pregnancy blood tests at 10 to 14 weeks may show a raised β-hCG, low plasma protein A and an increased nuchal translucency. A blood test performed at 14 to 20 weeks may show again a raised β-hCG and inhibin with a low AFP and unconjugated oestriol.