phoca_thumb_s_Transmission Ataxia telangiectasia (AT) or Louis-Bar syndrome is a rare, degenerative, hereditary disease that affects many parts of the body and causes severe disability. Ataxia means lack of coordination and telangiectasia are particularly visible blood vessels especially on the eyes.

AT associates a severe combined immunodeficiency - focusing mainly on humoral immunity - and a progressive cerebellar ataxia. It is characterized by an increased susceptibility to infections, neurological signs, telangiectasia and an increased risk of cancer.