Fig. 1

Renal biopsy histological features of PGNMID associated with multiple myeloma. First renal biopsy (a-k). a Periodic acid-Schiff (PAS) staining: renal histopathology showed lobular glomeruli with mesangial expansion and cell proliferation complicated with acute lesions, such as mesangiolysis, ×200. b Hematoxylin and eosin (HE) staining: glomerular micro-aneurysm and endocapillary hypercellularity, ×400. c Periodic acid methenamine silver (PAM) staining: duplication of glomerular basement membrane (an arrow) and mesangiolysis (an arrow head) was observed, ×1000. Congo red staining was negative (not shown). d Immunoglobulin G (IgG), e immunoglobulin G1 (IgG1), and f kappa immunostaining were detected on capillary walls and mesangial areas. (g) Lambda immunostaining was negative. h C3 immunofluorescence was positive (2+) on capillary walls, and (i) C1q was also weakly positive (1+) on some capillary walls. No positive immunofluorescence was found in tubular basement membranes. Staining for IgM and IgA was negative (not shown). IgG subclass analysis was positive for IgG1 only. IgG2, IgG3, and IgG4 were negative (not shown). EM (j) low-power and (k) high-power fields showed that electron-dense deposits in the subendothelial and mesangial areas exhibited a granular texture without a fibrillary appearance. Second renal biopsy (l-v). l Glomeruli showed less of an increase in mesangial matrix in the first renal biopsy and no mesangiolysis or micro-aneurysms with PAS staining, ×100. m A glomerulus showed no endocapillary hypercellularity with HE staining, ×400. n A glomerulus still had partial duplication of the glomerular basement membrane with PAM staining, ×1000. o IgG, (p) IgG1, (q) kappa, and (r) lambda immunofluorescence results were negative. (s) C3 immunofluorescence was weakly positive in a mesangial area. (t) No deposition of C1q. EM (u) low-power and (v) high-power fields showed no electron-dense deposits