Ataxia-telangiectasia is a multi-system disease that affects a startling variety of body systems.

It's important to note that A-T presents differently in each individual. There is high variability between people with A-T and even siblings with A-T. Not every child gets every symptom.

• Ataxia: The onset of this ataxia marks the beginning of progressive degeneration of a part of the brain, known as the cerebellum, that gradually leads to a general lack of muscle control, and eventually confines the patient to a wheelchair. Most A-T children are dependent on wheelchairs by the age of ten, not because their muscles are too weak, but because they cannot control them. Because of the worsening ataxia, children with A-T lose their ability to write, and speech also becomes slowed and slurred. Even reading eventually becomes impossible as eye movements become difficult to control.
• Telangiectasia: Soon after the onset of the ataxia, the A-T patient usually shows another clinical hallmark of A-T: “telangiectasia,” or tiny red “spider” veins which appear in the corners of the eyes or on the surface of the ears and cheeks exposed to sunlight. Although these telangiectasia are seemingly harmless, their unique appearance together with ataxia is what led to naming this disease “ataxia-telangiectasia.”
• Immune System Problems: For most (about 70 percent) of children with A-T there is another clinical hallmark: immunodeficiency that usually brings recurrent respiratory infections. In many patients, these infections can become life threatening. Because of deficient levels of immunoglobulins (IgG, IgA, IgM or IgG subclasses), the natural infection fighting agents in the blood, children with A-T are highly susceptible to lung infections that do not respond to typical antibiotic treatments. For these A-T patients, the combination of a weakened immune system and the progressive ataxia can ultimately lead to pneumonia as a common cause of death.
• Predisposition to Cancer: Children with A-T tend to develop malignancies of the blood system almost 1,000 times more frequently than the general population. Lymphoma and leukemia are particularly common types of cancer, although the frequencies of most cancers are elevated. Ironically, another facet of the disease is an extreme sensitivity to radiation, which means that A-T patients cannot tolerate the standard levels of therapeutic radiation or radiomimetic drugs (chemotherapy drugs that work in a way that is similar to radiation therapy) usually given to cancer patients.
• Other Features of A-T: Other features of ataxia-telangiectasia that may affect some children are: diabetes mellitus, premature graying of the hair, difficulty swallowing causing choking and/or drooling and slowed growth. Even though A-T is a multi-system disorder, most individuals with A-T are very socially aware and socially skilled.