is a kidney disease characterized by inflammation of the structures inside the kidney that help filter wastes and fluids. When the glomerular basement membrane becomes thickened, it does not work normally, allowing large amounts of protein to be lost in the urine. Symptoms develop gradually and may include swelling, fatigue, weight gain, and high blood pressure. In many cases, the underlying cause of membranous nephropathy is not known. Some cases are associated with other conditions (lupus), infections (hepatitis B and C), cancer or as a side effect of certain medications. The goal of treatment is to reduce symptoms and slow the progression of the disease. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.