A case of IgG4-related tubulointerstitial nephritis concurrent with Henoch-Schönlein purpura nephritis.

We describe a 72-year-old man, who had been suffered from Henoch-Schönlein purpura (HSP) several times, presented with hematoproteinuria with granular cast, and general lymphadenopathy. The immunological examination of the serum showed polyclonal hypergammagloburinemia with high value of IgG4. The renal biopsy revealed interstitial inflammatory cell infiltration, including infiltration of lymphocytes and plasma cells, and segmental glomerulonephritis. Direct immunofluorescence microscopy revealed apparent positive staining with anti-human IgA, and anti-human IgG in glomeruli, anti-human IgG4 antibody staining showed many positive plasma cells in the interstitium. The patient was diagnosed with HSP nephritis that was complicated by IgG4-related nephropathy. As a result of the treatment with 30mg prednisolone, the swelling of the LNs decreased, but the patient continued to have persistent hematoproteinuria.