Spontaneous remission in acute lymphoblastic leukemia: A rare phenomenon

Spontaneous remission in acute lymphoblastic leukemia (ALL) is a rare occurrence in which leukemia improves without adequate treatment. This phenomenon is often preceded by fever or septic episodes, though the underlying mechanisms remain unclear. We report the case of a 59-year-old female admitted to the Hematology Department with fever, chills and fatigue. Physical examination showed petechiae without lymphadenopathy or hepatosplenomegaly. Peripheral blood count showed anemia (hemoglobin 8 g/dL) and leucopenia (WBC 1.86x103 /µL) with 3% blast. Despite fever persisting for 5 days, the patient experienced progressive fatigue and excessive sweating over the following 2 weeks. Bone marrow aspiration and flow cytometry, performed due to persistent bicytopenia, demonstrated B-ALL L1 (86% blast) with a negative BCR-ABL mutation. Induction chemotherapy was planned; however, during preparation,the patient’s clinical symptoms and hematology profile improved spontaneously. Hemoglobin increased to 11.1 g/dL and WBC to 8.96 x103 /µL. A repeat bone marrow aspiration at 45 days revealed no blasts. The patient remained in remission with normal peripheral counts during 18 months of follow-up. Spontaneous remission in ALL is has been documented in fewer than 100 worldwide as of 2024. Most reported cases involve pediatric or young adult patients, with relapse occurring within 0 – 16 months (mean 7 months). Proposed mechanisms include apoptosis, endogenous or iatrogenic steroid effects, immune response to infection, and cytotoxic T-cell activity against leukemic cells. It hypothesized that pro-inflammatory cytokines and immune activation during severe infection shift the balance from pro-leukemia toward anti-leukemia, inducing temporary remission and hematopoietic recovery. Closing monitoring is essential due to relapse risk. Future studies are needed to understand the pathogenesis and determine the optimal maintenance strategy during remission.