Fig. 1
The renal biopsy specimen in case 1 contained 21 glomeruli, 4 with global sclerosis. a Periodic acid-Schiff (PAS) stain (100 ×) showed inflammatory cell infiltration in tubules and interstitium. b PAS stain (400 ×) showed infiltration of lymphocytes and plasma cells (yellow arrows) in interstitium. c Immunohistochemistry for IgM (400 ×) suggested existing IgM-positive plasma cells in tubules and interstitium. In three high-power fields (HPFs), the average number of IgM-PCs per HPF was 22. d Clinical course in case 1: After the patient started prednisolone (PSL; 30 mg daily; 0.45 mg/kg/day), markers decreased immediately, and we tapered and discontinued PSL as shown here. However, 1 month after PSL discontinuation, serum IgM (s-IgM), serum creatinine (s-Cr), urinary β2-microglobulin (u-β2MG), and proteinuria levels were elevated. Therefore, PSL 10 mg daily (0.15 mg/kg/day) was administered, and these markers improved