Large B-cell Lymphoma-Associated Membranous Nephropathy With Positive PLA2R on Kidney Biopsy

Large B-cell lymphoma associated with membranous nephropathy (MN) is a rare and complex medical condition that involves the simultaneous presence of two distinct diseases: a malignant lymphoma and a kidney disorder called membranous nephropathy. In this case, there is an additional element of interest, which is the presence of positive Phospholipase A2 Receptor (PLA2R) in the kidney. The case involves a 53-year-old Caucasian male with a three-week history of lower leg edema and a past medical history of recurrent upper respiratory infections. The upper respiratory infections were characterized by symptoms of fever, sore throat, and headache, and they required multiple rounds of antibiotics for treatment, including Augmentin and Keflex. A diagnosis of nephrotic syndrome was made based on proteinuria of fourteen grams with no RBC cast on urinalysis. Kidney biopsy stained positive for antiposophlipase A2 receptor on a frozen section. Thrombospondin type 1 domain-containing 7A (THSD7A) was not detected.  Given his biopsy and absence of clinical symptoms, he was treated as a case of primary membranous nephropathy with angiotensin-converting enzyme (ACE) inhibitors, steroids, and immunosuppressive. Three months following the treatment, his condition deteriorated, and after a thorough investigation, he appeared to have large B-cell lymphoma as a secondary cause of membranous glomerulopathy (MGN). When large B-cell lymphoma is associated with membranous nephropathy, it presents a unique clinical challenge. The interaction between these two conditions is not fully understood, but it is believed that the lymphoma may provoke an immune response that leads to the development of membranous nephropathy. Moreover, the presence of positive PLA2R in the kidney indicates a specific mechanism at play in this complex disease scenario. Treatment for this condition typically involves addressing both the lymphoma and the kidney disorder. This may include chemotherapy or other treatments to target the lymphoma and immunosuppressive therapy to manage the autoimmune response causing membranous nephropathy. Close monitoring and coordination between oncologists and nephrologists are essential for the best possible outcome in managing this rare and challenging condition.