13th March 2024

Pathophysiology

Down’s syndrome is the most common genetic cause of cognitive disability worldwide and occurs as a result of individuals having an extra copy of chromosome 21 (trisomy 21). It is associated with a range of dysmorphic features and a higher prevalence of medical conditions, including congenital heart defects. Around 95% of those with trisomy 21 are caused by chromosome non-disjunction. Less commonly, trisomy 21 is a result of chromosome translocation or mosaicism.

Diagnosis is most often through prenatal screening, although individuals may be diagnosed after birth through phenotypic features and genetic testing.