Background: Chronic Myelomonocytic leukemia (CMML) is a clonal hematopoietic malignancy and remains the most common overlapping myelodysplastic/ myeloproliferative neoplasm. Complications of CMML to acute monocytic leukemia transformation may include leukostasis, tumor lysis syndrome, and disseminated intravascular coagulation. We report a case that illustrates the disease characteristics and complications of CMML.
Case Report: A 76-year-old man, who was diagnosed 3 months prior to presentation with CMML, presented to the emergency department with dyspnea, altered mental status and right upper quadrant abdominal pain. His white count on admission was 314.5 × 109/L, which included 50 × 109/L blasts. His liver enzymes were elevated, and initial lactic acid was 12.5. No source of infection was found on imaging with Computed Tomography. Flow cytometry of peripheral blood revealed Acute Monocytic Leukemia. The diagnosis was consistent with CMML transformation to acute monocytic leukemia with hyperleukocytosis and leukostasis. He was started on cytoreduction therapy with hydroxyurea, leukapheresis, and decitabine chemotherapy. His symptoms improved with normalization of his white cell counts and he was discharged to concurrent hospice.
Discussion: Blast transformation (BT) to acute monocytic leukemia occurs in about 14% of patients diagnosed with CMML. 10-20% of newly diagnosed acute myeloid leukemia patients develop hyperleukocytosis (white cell counts greater than 100 x 109/L), a laboratory abnormality which may manifest clinically as leukostasis. Leukostasis, diagnosed empirically in a patient with BT who presents with respiratory and neurological symptoms, has 1-week mortality of 20%-40% if left untreated. Treatment of leukostasis includes leukapheresis, hydroxyurea, and induction chemotherapy. Recent studies have shown that leukapheresis reduces four-week mortality but does not affect long term mortality rate. More research is needed in understanding the pathophysiology of leukostasis, thus paving the way for novel therapeutic agents.
