Different clinical and immunological presentation of ataxia-telangiectasia within the same family.

Ataxia-telangiectasia is a rare multisystem neurodegenerative genetic disorder due to mutation of ATM gene. The clinical expression and the immunological abnormalities are variable and apparently not associated with the type of ATM mutations. We report on two siblings affected by A-T with different clinical and immunological presentations; in particular in one the immunological phenotype was reminiscent of hyper IgM syndrome.