TRANSFORMATION OF CHRONIC MYELOMONOCYTIC LEUKEMIA TO ACUTE MONOCYTIC LEUKEMIA IN AN ELDERLY PATIENT: A CASE REPORT

Abstract

Introduction: Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic disorder that exhibits both myelodysplastic and myeloproliferative features. Progression to acute monocytic leukemia is a notable complication, especially in elderly patients. This case report describes the transformation of CMML to acute monocytic leukemia in an 84-year-old male patient, emphasizing the importance of regular monitoring and timely intervention. Case report: M.O., an 84-year-old male, was diagnosed with CMML in August 2020. During a routine follow-up in July 2024, he presented with extensive bruising but no other apparent complaints. At the initial diagnosis, bone marrow studies revealed morphological abnormalities in granulocytic, erythroid, and megakaryocytic lineages with 2% blasts and 18% mature monocytes. Immunophenotyping showed 15.7% monocytic lineage cells, including 11.8% mature monocytes, 2.9% promonocytes, and 1.0% monoblasts and morphological dysplasia. Cytogenetic analysis identified a clone with deletion of part of the long arm of chromosome 20 in 2 out of 20 metaphases analyzed, with the remaining metaphases being normal (46,XY, del(20)(q12)[2]/46,XY[18]). The complete blood count (CBC) at diagnosis was Hb: 15.6 g/dL, WBC: 6,600/mm3 (Basophils: 66/mm3, Neutrophils: 3,102/mm3, Eosinophils: 66/mm3, Lymphocytes: 1,122/mm3, Monocytes: 2,244/mm3), and Platelets: 101,000/mm3. During the current visit in July 2024, CBC showed Hb: 11.5 g/dL, WBC: 9,400/mm3 (Basophils: 564/mm3, Neutrophils: 5,452/mm3, Lymphocytes: 1,222/mm3, Monocytes: 1,598/mm3, Blasts: 6%) with hypogranular neutrophils, and Platelets: 32,000/mm3. The presence of 6% blasts suggested disease progression. A repeat bone marrow examination confirmed disease evolution, showing massive infiltration by medium to large blasts with a moderate nucleocytoplasmic ratio, loose chromatin, basophilic cytoplasm, and frequent microvacuolizations with highly aberrant morphology. Immunophenotyping confirmed these cells to be immature with moderate CD45 expression and moderate internal complexity, exhibiting the following phenotype: positive for CD13 (weak), CD33 (strong), CD38 (strong), CD45 (moderate), CD56 (strong), CD64 (moderate), and cMPO (weak), and negative for cCD3, CD4, CD7, CD10, CD11b, CD14, CD16, CD19, CD34, cCD79a, CD117, CD123, IREM-2, and HLA-DR. Cytogenetic analysis revealed a clonal expansion with complex karyotyping (48,XY,+8,+8[12]/49,idem,+mar[3]/46,XY[5]). Discussion: The progression of CMML to acute monocytic leukemia is marked by an increase in blasts in both peripheral blood and bone marrow, along with notable changes in hematological parameters. This case demonstrates the transformation of CMML, corroborated by immunophenotyping and morphological studies. The presence of trisomy 8 and complex karyotype might be associated with a poor prognosis in CMML patients, often correlating with more aggressive disease and reduced overall survival. Identifying specific immunophenotypic markers is critical for diagnosing and differentiating acute monocytic leukemia. Conclusion: This case highlights the necessity of regular monitoring and timely reassessment of CMML patients. The transition to acute leukemia, a known complication, demands prompt diagnosis and intervention to manage the disease effectively.