Abstract
Background and Objectives
Ataxia telangiectasia is a disease with chromosomal instability that causes susceptibility to malignancy.
 
Case
The patient was a 7-year-old boy living in Shiraz who had ataxia telangiectasia and was hospitalized due to fever and lymphadenopathy. Bone marrow aspiration showed a 60% blast population that was consistent with acute T cell lymphoblastic leukemia, immunophenotypically. In cytogenetic examination of bone marrow aspiration, complex chromosomal abnormalities as 42,XY,-5,del(6)(q22),der(8)t(8;17)(q24;q12~q22),t(9;16) (q12;q24),dic(12;14)(p11;q24),+13,-14,-22 were observed. Despite chemotherapy, the patient expired after two relapses of leukemia.
 
Conclusions 
T cell acute lymphoblastic leukemia due to ataxia telangiectasia  can be associated with complex karyotype abnormalities leading to leukemia relapse and adverse prognosis.