Mercury Intoxication as a Rare Cause of Membranous Nephropathy in a Child

In adults, membranous nephropathy is the second most common cause of nephrotic syndrome. In contrast, minimal change disease and focal segmental glomerulosclerosis constitute the most common forms of nephrotic syndrome in children, while membranous nephropathy accounts for <5% of cases. In adults, causes of membranous nephropathy include autoantibodies directed against phospholipase A₂ receptor and thrombospondin type 1 containing 7A, various infections, environmental toxicities, autoimmune disorders, malignancies, and other secondary forms. The most common causes of secondary membranous nephropathy in children are infections, autoimmune diseases, and neoplasia. We discuss an unusual presentation of new-onset membranous nephropathy due to mercury toxicity in a 14-year-old male with reflux nephropathy. This case underscores the importance of a high index of suspicion for uncommon causes of nephrotic syndrome in pediatric patients with membranous nephropathy.