A Rare Case of Waldenström Macroglobulinemia Presenting as Bilateral Bloody Pleural Effusion and Pancytopenia.

BACKGROUND Waldenström macroglobulinemia (WM) is an uncommon, indolent mature B-cell lymphoma with various clinical manifestations. Bilateral bloody pleural effusion is rare, while chylothorax is even more infrequent. Furthermore, pancytopenia holds significant clinical relevance in WM, highlighting clinicians' need to exercise substantial vigilance. CASE REPORT We report the case of a 71-year-old man who was admitted for chest tightness, dyspnea, and fatigue. Initial laboratory tests revealed pancytopenia, and a computed tomography (CT) scan showed bilateral pleural effusion. The diagnostic workup included a lymph node biopsy that confirmed CD20+ B-cell lymphoma. Bone marrow molecular studies identified somatic mutations in MYD88 (L252P, c.755T>C) and CXCR4 (R322Sfs*16, c. 966-982del). The bone marrow biopsy indicated lymphoplasmacytic lymphoma. A serum immunofixation test revealed monoclonal bands of IgM and kappa. Based on the patient's symptoms and examination results, a thorough analysis led to the final diagnosis of Waldenström macroglobulinemia. The patient underwent therapeutic thoracentesis, followed by 4 cycles of rituximab (375 mg/m² on Day 1) and bendamustine (70 mg/m² on Days 2-3). Post-treatment evaluation revealed hematologic recovery and complete resolution of pleural effusions on thoracic ultrasound. CONCLUSIONS This case report elaborates on Waldenström macroglobulinemia's diagnosis and treatment process to enhance clinicians' awareness and ability to manage the complications associated with this rare disease.