Primary Renal Lymphoma: A Rare Cause of Bilateral Renal Enlargement and Acute Renal Failure in a Patient With Rheumatoid Arthritis.

Primary renal lymphoma (PRL) is a rare non-Hodgkin's lymphoma (NHL) involving the kidneys without evidence of extra-renal involvement. We describe a 66-year-old female who presented with bilateral pleural effusions, and acute renal failure and was diagnosed with primary renal diffuse large B-cell lymphoma (DLBCL). She presented with shortness of breath due to bilateral pleural effusions and acute renal failure. Computed tomography (CT) of the chest reported bilateral pleural effusions. Thoracocentesis and subsequent fluid analysis reported non-malignant effusion. Her kidney function worsened during her hospital stay, requiring dialysis. Nonspecific findings such as bilateral renal enlargement on imaging prompted a renal biopsy. Histopathology reported mixed tubulointerstitial atypical lymphocytic CD 20 and BCL-6 positive cell infiltrates, confirming non-Hodgkin diffuse large B-cell lymphoma. Whole-body positron emission tomography/CT (PET/CT) and brain magnetic resonance imaging (MRI) ruled out the involvement of any other organs or lymph nodes, confirming our diagnosis of PRL. She was treated with six cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). Her kidney function recovered fully and remained normal at the one-year follow-up. We highlight the importance of recognizing PRL as an underlying cause of renal failure and its association with autoimmune diseases. Prompt investigation with timely diagnosis and treatment can result in improved morbidity and mortality in these patients.