(1138) Leukostasis in Chronic Myelomonocytic Leukemia Causing Pleural Effusion & Acute Respiratory Failure

Introduction: Chronic myelomonocytic leukemia (CMML) accounts for less than 1% of all hematological malignancies. Pulmonary leukemic infiltration is a major clinical consideration seen in 25% of cases. Serous effusions like pleural effusion is a rare complication of CMML and is present only in 1.7 % of patients. We report a rare case of CMML presenting with pleural effusion and acute hypoxic respiratory failure secondary to leukostasis as the primary manifestation.

Description: A 74-year-old male presented with progressive shortness of breath, fatigue, loss of appetite for the past 1 month. Initial lab work showed anemia with hemoglobin of 8.6 g/dl, thrombocytopenia with platelet count of 108 and leukocytosis with WBC count of 52000. Imaging showed interstitial infiltrates, bilateral pleural effusions, splenomegaly. The patient was started on broad spectrum antibiotics with no improvement, respiratory status deteriorated requiring BiPAP and the WBC count worsened to 77000 with 28.9% monocytes. Thoracentesis revealed exudative effusion with abundant acute inflammation and inflammatory exudate. The pleural effusion was bloody with abnormal monocytic population concerning for a myeloid neoplasm. Bone marrow biopsy revealed myeloproliferative neoplasm consistent with CMML. He continued to deteriorate despite full respiratory support, the WBC count increased to 124,000 and the patient expired after 7 hours of mechanical ventilation.

Discussion: Chronic myelomonocytic leukemia is a rare hematological malignancy with incidence estimated to be around 4 cases per 100,000 persons per year. It usually presents in the 7th decade of life with male predominance and overall survival of < 36 months. Pulmonary complications with leukemia are generally secondary to infection, hemorrhage, drug toxicity and leukostasis. Leukemic pulmonary infiltration results from collection of leukemic cells in the lung parenchyma and pleura, and is usually accompanied by rapid rise in leukocyte count. It presents as a rapid decline in respiratory status and WBC count > 100,000. Recognizing this complication and treating it appropriately may reduce mortality and morbidity. Allogeneic stem cell transplantation is the only curative treatment but most individuals remain ineligible due to late onset of this neoplasm.