A variety of renal disorders can occur in patients with rheumatoid arthritis (RA), due to the underlying disease, to drugs used to treat the inflammatory process, and to concurrent renal disease unrelated to RA, which is more likely in elderly patients with significant comorbid conditions.
The most common disorders associated with RA are membranous nephropathy, secondary amyloidosis, a focal, mesangial proliferative glomerulonephritis, rheumatoid vasculitis, and analgesic nephropathy [1,2]. Other disorders, such as IgA nephropathy and minimal change disease have also been reported in patients with RA, although this may represent coincidental disease [1,2].
The reported prevalence of chronic kidney disease (CKD) in patients with RA has varied between 5 and 50 percent in different series . In the Methotrexate And Renal Insufficiency (MATRIX) study of 129 patients, 20 percent of patients had an estimated glomerular filtration rate (eGFR) of 60 to 89 mL/min per 1.73 m2, and 15 percent had an eGFR of 30 to 59 mL/min per 1.73 m2 . CKD may be due to renal diseases associated with RA, which are discussed below, or to concurrent renal disease.
The formulas used to calculate the eGFR (Cockcroft-Gault and MDRD) contain the serum creatinine, which must be stable, and factors that affect muscle mass (lean body weight, age, gender, and race) and therefore affect the serum creatinine independent of GFR. (See "Assessment of kidney function".)
The history (such as the use of gold or penicillamine) and timing of the onset can usually help to distinguish among the different causes of renal disease in patients with RA. As an example, only patients with chronic active arthritis are at risk for secondary amyloidosis, although membranous nephropathy can also occur in this setting. In contrast, membranous nephropathy is much more likely when proteinuria develops after a period of quiescent disease that is frequently drug-induced.