In 1941 Louis-Bar41described an isolated case of progressive cerebellar ataxia associated with oculocutaneous telangiectasia. This syndrome became well known with the publication of eight cases of Boder and Sedgwick12in 1958. The latter authors gave the name ataxia-telangiectasia (AT) and added the third major component of the syndrome, recurrent severe sinopulmonary infection. They also emphasized the familial nature of the disease. The neurological manifestations of AT are usually the first to appear. Abnormalities are often detectable when the child begins to walk or even earlier. Two features, in addition to progressive cerebellar signs, are characteristic of the neurological picture: (1) choreic and athetoid movements were responsible for the title chosen by Wells and Shy75for their report in 1957: "Progressive familial choreoathetosis with cutaneous telangiectasia," and (2) pseudopalsy of the eyes which has been likened to oculomotor apraxia is present in most cases.66The patient is