Skin Fairness Cream-Associated NELL-1 Membranous Nephropathy Treatment With Mercury Chelation and Immunosuppressive Therapy: An Educational Case Report.

Case Description: A 38-year-old man presented with NELL-1 positive membranous nephropathy (MN). Initial treatment with rituximab and later cyclosporine failed to result in sustained clinical improvement. Upon further review, the patient had been applying a skin fairness cream nightly for 2 years preceding diagnosis. The cream was discontinued, and follow-up testing confirmed markedly elevated serum mercury levels of 66.8 µg/L (normal less than 20 µg/L), and 24-hour urine mercury of 103.9 nmol/d. Two rounds of chelation therapy were arranged, the first with dimercaptosuccinic acid (DMSA) and the second with dimercaptopropane-1-sulfonic acid (DMPS) given cost and availability. Repeat mercury levels normalized but follow up kidney biopsy confirmed persistent immune complex glomerulonephritis. The patient was subsequently treated with prednisone followed by additional rituximab resulting in improvement of proteinuria and stabilization of kidney function. Rationale/Teaching Points: This case reinforces the risk of mercury containing topicals and is the first to report systemic absorption of this magnitude. While chelation therapy is effective at improving systemic mercury levels, patients may require additional immunosuppression to treat immune complex-mediated MN following exposure.