Ataxia-telangiectasia (A-T) is a primary immunodeficiency disease which affects a number of different organs in the body. An immunodeficiency disease is one that causes the immune system to break down, making the body susceptible to diseases. It is a rare, recessive genetic disorder of childhood that occurs in between 1 out of 40,000 and 1 out of 100,000 persons worldwide. The ailment is progressive. Patients with A-T are frequently wheelchair-bound by their teens, and the disease is generally fatal to patients by the time they reach their twenties.