A congenital disorder is a medical condition that is present at birth. Congenital disorders can be a result of genetic abnormalities, the intrauterine environment, or unknown factors. Sickle cell disease [a group of genetic disorders caused by sickle haemoglobin (HbS).HbS molecules tend to clump together, making red blood cells sticky, stiff and more fragile and causing them to form into a curved, sickle shape ] and Huntington's chorea (an inherited disorder characterised by degenerative changes in the basal ganglia structures, which ultimately result in a severely shrunken brain and enlarged ventricles, abnormal body movements called chorea and loss of memory) are congenital disorders.