INTRODUCTION
The current treatment regimens for acute lymphoblastic leukemia (ALL) have successfully attained cure-rates of approximately 90-95% in children, but still with poor overall long-term survival in adults of about 40% 1-3. It still remains a significant challenge to improve the survival of patients with relapsed ALL. Patients with relapsed ALL have a suboptimal prognosis1, 4. Down syndrome patients (DS) with relapsed ALL have even worse outcomes. DS itself was proven to be an independent prognostic factor of outcome after ALL relapse.5 ALL patients with DS have a higher rate of relapse and treatment related mortality, with an 8-year cumulative incidence of relapse of 26% comparing with 15% in non-DS patients and a 2-year treatment-related mortality of 7% with 2% in the latter.6 There are several case reports of patients with leukemia who attained spontaneous remission after severe infection 7-9. There are no reports of a patient with relapsed leukemia with sustained remission following cessation of therapy secondary to severe infections, except an older patient with relapsed FLT3 internal tandem duplication mutant acute myeloid leukemia whose disease underwent spontaneous remission for 35 days without precipitating cause 10.
We describe a case of a 37 year-old man with Down syndrome and ALL (DS-ALL) who had a late bone marrow relapse and sustained remission for 2 years after only receiving two cycles of ALL R3 salvage chemotherapy due to severe systemic infections.