The present invention relates to a novel procedure for evaluating the response of patients affected by Ataxia Talangiectasia (A-T) to glucocorticoids treatment. In particular, the procedure provides a step of qualitative and/or quantitative identification in the blood of said patients of the expression of a mRNA variant of the ATM (Ataxia-Talangiectasia-Mutated) gene produced by non-canonical splicing induced by glucocorticoid (GC). In fact, it was demonstrated that mRNA variant expression is present in the blood of patients who responded positively to treatment with GC.
