Diagnostic Pitfalls of Chylothorax After Dasatinib Treatment of Chronic Myeloid Leukemia

BACKGROUND Chronic myeloid leukemia (CML) is a myeloproliferative malignancy generally treated with Dasatinib, a tyrosin-kinase inhibitor. Pleural effusions are a known adverse effect, but only 0.8% of patients develop pleural effusions after 6 years of use. Recent case reports have implicated Dasatinib as a rare cause of chylothorax. CASE REPORT We describe a woman in her 30's with a history of chronic myeloid leukemia, who had been taking Dasatinib for 10 years and presented to the Emergency Department after a chest X-ray revealed bilateral pleural effusions in the setting of worsening dyspnea on exertion for 6 months. She had previously received radiotherapy at age 11 prior to an allogenic bone marrow transplant nearly 30 years prior. Thoracentesis removed 900 cc of chylous fluid, and flow cytometry and cultures found no evidence of infection or malignancy. Dasatinib was discontinued, and she was treated with diuretics, steroids, and a low-fat diet. The effusions reaccumulated twice in the following month and required 2 additional thoracenteses and courses of steroids. Months later, the bilateral chylous effusions recurred, and MR lymphangiogram demonstrated 2 thoracic duct tears. CONCLUSIONS While previous reports have indicated that Dasatinib can rarely cause chylous pleural effusions, it is unlikely after 5 years of use, and other etiologies must be considered by clinicians. Initial misattribution to Dasatinib alone can delay further necessary investigations, including lymphangiography. In our patient, it is more likely that other factors contributed to her chylothorax, including her previous radiotherapy 30 years prior, given her recurrence of chylous effusions following cessation of the medication.