Mesangiocapillary glomerulonephritis with dense "deposits" in the basement membranes of the kidney.

Amongst 125 patients with mesangiocapillary glomerulonephritis (MCGN), 19 showed continuous intramembranous dense "deposits" (IDD). Most were children or young adults. Two patients had partial lipodystrophy. Eleven had a consistently low plasma concentration of C3; only three, however, had an initial low plasma concentration of C4, which rose and then remained normal in two. Tests for the C3 nephritic factor were positive in thirteen patients, and plasma C1q was normal in 8 out of 11 cases investigated. Ten out of twelve (seven of them with low plasma C3) showed C3 deposition by immunofluorescence in the glomerular tuft. This was also demonstrated in some instances in Bowman's capsule and tubular basement membranes. Stains for IgG, IgA, C4 and C1q were negative in all, whereas stains for IgM and fibrin were weakly positive in the glomeruli of three and eight cases repectively. Eight patients went into terminal renal failure over an average of thirty-three months and required hemodialysis or transplantation. MCGN with IDD is an uncommon pattern of renal response to injury, which involves activation of the alternate pathway of the complement system and has a poor short term prognosis. The association with partial lipodystrophy and C3-splitting activity suggests a primary complement abnormality.