Renal disease is not uncommon in patients with rheumatoid arthritis, and the differential diagnosis is quite interesting. Here is a list of the major causes, some of which are caused by the RA itself and others of which are caused by the common medications used to treat RA:
-Amyloidosis- of the AA variety, due to a persistently active pro-inflammatory state.
-Membranous Nephropathy- a secondary nephrotic syndrome may occur due to RA, or due to treatment with the RA drugs gold and penicillamine.
-Analgesic nephropathy-this can be seen due to the high, chronic doses of salicylates and/or NSAIDs used for the chronic joint pain that is a hallmark of RA.
-Focal mesangial proliferative glomerulonephritis-which may be recognized based on a nephritic urine sediment. -Rheumatoid vasculitis- this is a rare complication of RA which may affect the small- and medium-sized arteries. It is somewhat similar in its manifestations to polyarteritis nodosa (PAN) and occasionally (though not always) involves the kidneys.
I saw a patient in clinic today with a long-standing history of JRA who a few months back developed RPGN...a renal biopsy had shown a combination between an immune complex GN, endothelial injury likely 2/2 malignant hypertension, and podocyte foot process effacement which was causing nephrotic syndrome...illustrating the fact that patients with RA may be susceptible to other forms of autoimmune disease and may have complex, overlapping diagnoses which are not straightforward.