Understanding Primary Membranous Nephropathy: A Comprehensive Look at Diagnosis and New Treatments
Primary membranous nephropathy (PMN) is an autoimmune kidney disease that most people have never heard of, despite being the most common cause of a condition called nephrotic syndrome in non-diabetic adults. In PMN, the immune system produces antibodies that mistakenly attack proteins on cells in the kidney's filtration system, leading to protein leakage into the urine, swelling, and eventually potential kidney failure if left untreated. A thorough review published in Frontiers in Immunology in June 2026 by researchers at Thomas Jefferson University brings together the latest science on what causes this disease and how it can be treated.
The most common target of these misguided antibodies is a protein called phospholipase A2 receptor (PLA2R), found on specialized kidney cells called podocytes. Roughly 70 to 80 percent of primary cases involve PLA2R antibodies, and doctors can now test for these antibodies in the blood, making diagnosis less invasive than relying entirely on kidney biopsies. Fourteen other target antigens have been identified in recent years, though in about 5 to 10 percent of cases, the target protein remains unknown.
What happens to patients varies widely. About one-third of people with PMN will experience spontaneous remission without any immunosuppressive treatment, meaning their immune system corrects itself. Another third will have progressive kidney decline that may eventually require dialysis or transplant. The remaining third live with persistent protein leakage in the urine but maintain relatively stable kidney function over time. This variability makes deciding when and how aggressively to treat a real clinical challenge.
Current guidelines recommend risk-stratifying patients before reaching for immunosuppression. Low-risk patients, particularly those with modest protein losses and stable kidney function, can often be monitored carefully without treatment. High-risk patients, especially those with rapidly declining kidney function or severe protein loss causing complications, may be offered older regimens alternating steroids with cyclophosphamide. However, the landscape has shifted substantially toward rituximab, a drug that depletes the B cells responsible for making the damaging antibodies. Studies show that rituximab produces remission in 60 to 80 percent of patients and is now widely considered the preferred first-line immunosuppressive therapy.
One of the most useful aspects of the PLA2R antibody test is that antibody levels can be monitored over time to assess treatment response. Importantly, the antibodies often disappear from the blood months before the protein leakage in the urine clears up, which means patients and doctors need to be patient when interpreting results. Rising antibody levels after remission can signal an impending relapse, offering an opportunity for early intervention.
Not everyone responds to rituximab, and the review discusses emerging strategies for rituximab-resistant cases. These include using more potent B-cell depleting antibodies such as obinutuzumab or ofatumumab, as well as newer approaches targeting plasma cells (the antibody-producing cells downstream of B cells) using drugs like daratumumab or felzartamab. Anti-complement therapies and agents blocking APRIL and BAFF, proteins that support the survival of antibody-producing cells, are also under investigation.
For patients who have reached end-stage kidney disease, transplantation remains the best option. However, PMN can recur after transplant, and doctors now have guidance on using antibody levels to guide decisions about preventive treatment in PLA2R-positive patients. The science of PMN continues to evolve rapidly, offering genuine reason for optimism that increasingly targeted and better-tolerated therapies are on the horizon.