Drug-associated glomerulopathies

The renal glomeruli are vulnerable to injury by a number of drugs and other toxic agents. These agents may lead to damage by one of two basic mechanisms: direct, dose-related toxic injury; indirect, immunologically mediated injury, largely dose-independent. Proteinuria is the simplest and most important functional indicator of glomerular injury. It occurs almost immediately in direct toxic injury, but there is a latent period of weeks to months with immunologically mediated processes. Of the two mechanisms, the second is by far the more common in clinical settings. The best studied experimental agent causing direct toxic injury is the aminonucleoside of puromycin. Clinically, perhaps the most important agent is Cyclosporine A. Although this agent is usually thought of primarily as a tubular toxin, it is capable of giving rise to a microangiopathic glomerular lesion similar to that in the hemolytic uremic syndrome. The classic model for immunologic glomerular lesion is Heymann nephritis, which produces a membranous glomerulopathy. Clinically, most drug mediated glomerulopathies also take the form of a membranous nephropathy, usually with a frank nephrotic syndrome. Among the more common offenders are penicillamine, gold salts used in rheumatoid arthritis, and captopril used in hypertension. The other common type of drug-related glomerulopathy occurs as part of a lupus-like syndrome induced by a variety of drugs, including hydralazine, procainamide, and penicillamine. All of these give rise to a variety of antibodies, most prominently antinuclear antibodies, and in the more severe cases there may be lupus-like glomerular lesions as well.