Secondary myelodysplasia with monosomy 7 arising after treatment for acute lymphoblastic leukemia in childhood.

Monosomy 7 is recognized as a characteristic, clonal abnormality associated with acquired myelodysplasia (MDS) or acute myeloid leukemia (AML). It can occur as a late complication of cytotoxic therapy and is usually associated with exposure to alkylating agents or radiation therapy. We report two patients with therapy-related myelodysplasia (t-MDS) associated with monosomy 7 occurring in children after completion of therapy for acute lymphoblastic leukemia (ALL). Both children were noted to have t-MDS with monosomy 7 at the time of cessation of chemotherapy. Neither child had received an alkylating agent or radiation therapy during treatment. One child had a unique dicentric marker chromosome that was shown by fluorescent in situ hybridization to be derived from chromosome 7. This report emphasizes the need to identify and minimize therapy-related side effects without compromising cure rates.