What part of the body does down syndrome affect?

All of it: The chromosome defect is present in every cell of the body. It may or may not produce abnormalities in the formation of major or minor organs like the heart / abnormalities in the function of organs like the brain. Over a lifetime the body structure is affected by weaknesses in bony structure & muscle tone. Vulnerability to various illnesses is increased.

Whole body: Individuals with Down syndrome have the extra chromosome in every cell of the body. There is a high incidence of heart and other organ systems that are affected

Every cell: The defect of DS is triggered by an extra chromosome in every cell of the body.Sometimes this will result in a heart defect, sometimes not.It usually effects the formation of facial structures,making many appear similar, other problems can emerge as they grow older, like scoliosis, a tendercy toward thyroid problems, etc.