Comparison of idiopathic and systemic lupus erythematosus-associated membranous glomerulonephropathy in children. The Southwest Pediatric Nephrology Study Group.

This retrospective multicenter study has revealed 68 children with membranous glomerulonephropathy (MGN), accounting for 5.5% of all patients (pts) with nephrotic syndrome who were biopsied during the period of study. The total group includes 54 pts with idiopathic MGN (IMGN), 10 with lupus MGN (LMGN), and 4 who were ANA-positive but had no other features of systemic lupus erythematosus (SLE). Renal biopsies were examined by light (LM), immunofluorescent (IF), and electron microscopy (EM), and the findings compared with clinical features within and between the IMGN and LMGN groups. The LMGN pts tended to be more frequently female and older, and differed significantly from the IMGN pts by being more frequently hypocomplementemic (70% v 4%, p less than 0.001), and having higher levels of total serum protein (6.6 +/- 1.2 v 5.1 +/- 1.0, p less than 0.03), and serum albumin (2.9 +/- 0.7 v 2.2 +/- 0.8, p = 0.03). There was no significant difference in glomerular filtration rate (GFR) or the frequency of hypertension or hematuria between the two groups. Pathologic features that differed between LMGN and IMGN included diffuse mesangial hypercellularity (44% v 7%, p = 0.01), glomerular electron-dense subendothelial deposits (78% v 13%, p = 0.001), and mesangial deposits (100% v 31%, p = 0.002). The frequency of focal mesangial hypercellularity and of mesangial sclerosis, tubulointerstitial disease, and frequency of glomerular immunoreactants did not differ between the groups. Limited follow-up of the pts has revealed no difference in outcome between the IMGN and LMGN pts. We conclude that differentiation between IMGN and LMGN in children, as in adults, may be difficult on pathologic grounds alone and that the separation can only be made by established clinical and laboratory criteria of SLE.