MESANGIAL GLOMERULONEPHRITIS AS AN EXTRAARTICULAR MANIFESTATION OF RHEUMATOID-ARTHRITIS

Mesangial glomerulonephritis (MesGN) is a frequent renal biopsy findin g in patients with rheumatoid arthritis (RA) presenting with haematuri a and/or proteinuria. The purpose of this study was to describe the me sangial immunofluorescence (IF) findings in 37 such RA patients, and t o correlate the nature of the glomerular immunodeposits with clinical data, levels of serum immunoglobulins and the concentrations of serum rheumatoid factors (RFs). The serological findings in RA patients with MesGN were correlated with those of RA patients matched for age, sex and duration of RA, but without clinically evident renal disease. The most characteristic mesangial IF finding in 37 RA patients with MesGN was ISM observed in 29 specimens (78%). IgA (n = 16) and C3 (n = 15) d eposits were also frequently found, whereas Clo (n = 3) and IgG (n = 2 ) deposits were only occasionally seen. Two main patterns of IF findin gs could be classified. (1) Granular IgM deposits as a sole or main fi nding (IgM GN; 25 specimens). The intensity of the mesangial IgM depos its did not correlate with the duration or severity of RA nor with the levels of serum immunoglobulins. However, a significant correlation w ith the intensity of mesangial IgM deposits and the levels of serum Ig M class RF was observed. (2) Granular IgA deposits usually together wi th the complement component C3, i.e. IEA glomerulonephritis (IgA GN; n ine specimens). The intensity of mesangial ISA deposits correlated sig nificantly with the duration and severity of RA, and especially with s erum IgA levels. Both RA patients with IgA GN or IgM GN were associate d with a more frequent occurrence and higher titres of serum RFs when compared with the RA patients without nephropathy. The clinicopatholog ical correlations and the association with RF support the concept that MesGN is related to the basic rheumatoid disease, and ic should be re garded as an extra-articular manifestation of RA.