Severe Pancytopenia After COVID-19 Revealing a Case of Primary Bone Marrow Diffuse Large B Cell Lymphoma

BACKGROUND Diffuse large B cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL). While bone marrow (BM) involvement is common in lymphoma, primary bone marrow (PBM) DLBCL is extremely rare. We present a case of PBM DLBCL discovered in a patient with COVID-19. CASE REPORT An 80-year-old man presented with generalized abdominal pain, weight loss, fever, fatigue, anorexia, and watery diarrhea over a 3-month period. Physical examination was unremarkable. Laboratory workup revealed anemia, thrombocytopenia, and elevated inflammation markers. SARS-COV-2 PCR was positive, while blood cultures were negative. A rapid decline in the white blood cell count in the following days prompted a BM biopsy, confirming the diagnosis of PBM DLBCL. Computed tomography (CT) did not show thoracic or abdominal lymphadenopathy. The patient received packed red blood cell and platelet transfusions, granulocyte colony-stimulating factor (G-CSF) for pancytopenia, and empirical antibiotics for suspected infection. Due to active COVID-19 and advanced age, cytotoxic chemotherapy was delayed. Rituximab and prednisone were initiated on day 9, followed by an infusion reaction, which led to treatment discontinuation. He died 2 days later. CONCLUSIONS Diagnosing PBM malignancy is challenging, especially with coexisting infection. It is essential to suspect underlying BM malignancy in patients with clinical deterioration and worsening pancytopenia despite adequate treatment. The diagnosis of PBM DLBCL requires the absence of lymphadenopathy, and the presence of histologically confirmed DLBCL. Prompt management with combination chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) with/without hematopoietic stem cell transplant can improve the prognosis.