[Clinico-genetic diagnosis of ataxia telangiectatica (Louis-Bar syndrome)].

We describe the possible difficulties in getting the diagnosis "ataxia telangiectasia" using the example of a 16 years old girl. If cases of cerebellar ataxia in childhood present without classical symptoms, the diagnosis of ataxia telangiectasia should not be excluded before chromosome analysis. In our case, first signs of cerebellar ataxia were observed from the age of 11 years and we found only mild, atypical located and late onset telangiectasis. Other signs of the syndrome, such as elevated alpha-fetoproteine and deficiency of IgA or IgE could not be detected. Chromosome analysis, however, demonstrated a breakage syndrome with chromosome 14 to 7 translocation and established a firm diagnosis of ataxia telangiectasia. Patients with chromosome breakage syndromes including the Louis-Bar-syndrome have an increased risk for malignomas. Therefore chromosome analysis should be undertaken in cases of children with cerebellar ataxia, and frequent radiological examination avoided.