Down syndrome or Down's syndrome is associated with several complications and health conditions that may require special medical care and support. Some of these conditions such as heart defect may be present from birth, while others such as epilepsy or intestinal problems may emerge over time. Some of the complications associated with Down syndrome are described below.

Congenital heart disease
Nearly half of Down syndrome sufferers are born with a heart defect, requiring hospitalization and treatment in about 60% of cases. Almost all of those who are born with a heart defect have a septal defect, which is a whole in the wall that separates the left and right chambers of the heart. The condition is commonly referred to as a “hole in the heart.” Other less common heart defects seen in Down syndrome include tetralogy of Fallot and patent ductus arteriosus.

Leukemia
Leukemia is significantly more common among children suffering from Down syndrome than among those in the general population. In particular, the risk of acute lymphocytic leukemia and acute myeloid leukemia is higher among these children. The condition has also been linked to an increased risk for transient leukemia, a condition similar to leukemia that arises in the first month of life but resolves independently of treatment at a later stage.

Thyroid disease
People with Down syndrome are at an increased risk of either underactive thyroid (hypothyroidism) or overactive thyroid (hyperthyroidism). Those with an underactive thyroid may feel lethargic, gain weight and have delayed physical and mental responses, while those with an overactive thyroid may suffer from hyperactivity and have difficulty sleeping.

Infertility
Another complication associated with Down syndrome is infertility. Only around 30% to 50% of females are estimated to be fertile and the menopause usually occurs at an earlier age than in the general population. Males with the condition do not usually father children, although it is unclear whether the cause is poor sperm development or lack of sexual activity.

Intestinal problems
Many individuals with Down syndrome experience intestinal problems. Examples include constipation, indigestion, diarrhea and obstruction of the bowel. Around 5% to 15% of people with the condition also develop celiac disease. Some children may be born with a condition called imperforate anus (the absence of an anal opening) or Hirschsprung’s disease, which affects the large bowel’s ability to move feces along towards the anus.

Vision problems
Nearly 50% of Down syndrome sufferers find they have visual disturbances such as a squint, lazy eye, short or long sightedness, cataract, keratoconus (thin and bulging cornea) or nystagmus (uncontrolled eye movements).