DiGeorge syndrome (DGS), also called DiGeorge anomaly or thymic aplasia, is an immune system disorder that occurs when the thymus gland is absent or not fully developed. Patients are born with this disorder.

The thymus gland is responsible for producing white blood cells called T-cells, which help the body fight against disease and infection. When the thymus gland is absent or underdeveloped, not enough T cells are produced. Therefore, patients with DGS syndrome are vulnerable to infections.

This disorder is also associated with other developmental defects, including abnormalities of the heart and large blood vessels around the heart and face. In addition, DGS patients often have underactive parathyroid glands (hypoparathyroidism) and the tube that leads from the mouth to the stomach (esophagus) is typically underdeveloped.

Depending on how underdeveloped the parathyroid gland is, some patients may experience low calcium levels in the blood, which may lead to seizures. This is because the parathyroid gland is responsible for regulating the body's calcium levels.

The condition is caused by a genetic defect. DGS patients are missing a specific chromosome. The chromosomes contain the genetic makeup of an individual. In a minority of cases, the defect is inherited (passed down from parents to their children). In most cases, patients are born without the gene by chance.

Researchers estimate that about one out of 3,000-4,000 individuals are born with DGS worldwide. Men and women are equally affected by DGS.

The disorder is usually diagnosed soon after birth because of the distinct physical defects and heart abnormalities associated with it.

There is currently no cure for DiGeorge syndrome (DGS). Thymus gland and bone marrow transplants have been conducted with varying effectiveness. Patients typically receive supplements with calcium and vitamin D to manage their underactive parathyroid glands.

The prognosis varies among patients. Some patients who have partial DGS may experience spontaneous T-cell improvement and parathyroid function. However, most patients with complete DGS die within the first six months of life. Most deaths are the result of heart defects. Infections caused by severe immune deficiency are the second most common cause of death.

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