Down Syndrome

47,XX,+21; 47,XY,+21; Trisomy 21

Down syndrome (also Down's syndrome) or trisomy 21 is a genetic condition resulting from the presence of all or part of an extra 21st chromosome. Down syndrome is characterized by a combination of major and minor abnormalities of body structure and function. Among features present in nearly all cases are impairment of learning and physical growth, and a recognizable facial appearance usually identified at birth. It is named after John Langdon Down, the British doctor who first described it ...