Abnormal condition, marked by edema, the presence of large amounts of protein in the urine, and lower than normal levels of albumin in the blood. Often accompanied by nausea, weakness, and loss of appetite, it is usually associated with disease of the glomerulus (glomerulonephritis) or occurs as a complication of many systemic diseases (e.g., multiple myeloma, diabetes mellitus, systemic lupus erythematosus).