Post-induction bone marrow uncovers mastocytosis in a case of acute myeloid leukemia-Case report

Acute myeloid leukemia (AML) with the RUNX1::RUNX1T1 fusion is typically associated with a favorable prognosis. However, when it occurs alongside systemic mastocytosis (SM), the outcome is usually adverse. This report describes a case involving a 41-year-old male diagnosed with AML harboring the RUNX1::RUNX1T1 fusion, who was initially misdiagnosed due to the lack of a thorough bone marrow examination. Although molecular testing confirmed the RUNX1::RUNX1T1 fusion, the associated mast cell component was overlooked, as the initial evaluation focused on peripheral blood. Follow-up bone marrow aspiration revealed an increased population of spindle-shaped mast cells, leading to a revised diagnosis of systemic mastocytosis with associated hematological neoplasm (SM-AHN) upon detection of a C-KIT D816Y mutation. This case emphasizes the necessity for comprehensive diagnostic evaluations, including bone marrow analysis and molecular testing for KIT mutations, to accurately identify concurrent neoplasms. While AML with RUNX1::RUNX1T1 fusion generally has a favorable prognosis, the presence of systemic mastocytosis and KIT mutations complicate the clinical landscape, requiring careful monitoring and potential modification of therapeutic strategies.