Abstract
RATIONALE: The rare t(3;21)(q26;q22) translocation results in gene fusion and generates multiple fusion transcripts, which are typically associated with therapy-related myelodysplastic syndrome, acute myeloid leukemia, and chronic myelogenous leukemia. Here, we report a rare case of de novo acute myelomonocytic leukemia in a young child with t(3;21)(q26;q22). PATIENT CONCERNS: A 2-and-a-half-year-old female patient presented with abdominal pain, cough, paleness, and fever for 3 weeks, without any history of malignant diseases. DIAGNOSES: Chest computed tomography revealed pneumonia. Bone marrow smear confirmed acute myelomonocytic leukemia. Cytogenetic analysis and Sanger sequencing identified RUNX1-MECOM and RUNX1-RPL22 fusion genes as a result of t(3;21)(q26;q22). INTERVENTIONS: The patient received 3 courses of chemotherapy, but bone marrow smear examination showed no remission. According to the wishes of the patient family, the allogeneic hematopoietic stem cell transplantation (Allo-HSCT) was chosen. OUTCOMES: The patient did not experience any adverse reactions after Allo-HSCT. The red blood cells and platelets increased without transfusion. The pneumonia recovered after antibiotic treatment. LESSONS: The patient recovered well after Allo-HSCT. Therefore, for patients with RUNX1-MECOM and RUNX1-RPL22 fusion genes, transplantation may be a good choice when chemotherapy is not effective.