IgG4-related acute interstitial nephritis and the potential role of mCRP autoantibodies: a case report

Abstract

Background: IgG4-related acute tubulointerstitial nephritis is a type of autoimmune-mediated interstitial nephritis. Recently, autoantibodies against modified C-reactive protein (mCRP) were found to play a pathogenic role in renal diseases through the formation of tubulointerstitial lesions. This is the first case report on the presence of mCRP autoantibodies in a patient with IgG4-associated acute tubulointerstitial nephritis. Case presentation: A 70-year-old man was admitted with renal dysfunction and a medical history of bile duct stenosis, an inflammatory pancreatic mass, hypertension, and diabetes. On admission, laboratory tests showed higher than normal levels of serum creatinine and IgG4 and lower than normal levels of complements 3 and 4. In addition, the mCRP autoantibody levels were elevated, and the findings of kidney biopsy revealed interstitial nephritis with rich plasma cells in the renal interstitium. The patient was administered prednisone and cyclophosphamide therapy, which resulted in a rapid improvement in renal function. Conclusion: IgG4-related autoimmune disease should be considered in the diagnosis of patients who have tubulointerstitial nephritis with multisystem involvement. Further, mCRP autoantibodies may be associated with IgG4-related tubulointerstitial nephritis and might be useful as a diagnostic marker of the disease.

Keywords: IgG4-related disease; acute interstitial nephritis; acute kidney failure; mCRP autoantibodies.

Figure 1.

Pathological features of the renal biopsy specimen. (a) The tubulointerstitium shows marked injury, but the glomerulus shows no specific features (Masson trichrome staining, ×100). (b) Storiform fibrosis with tubular atrophy can be observed in the tubulointerstitium (Masson trichrome staining, × 200). (c) A mass of inflammatory cells, including lymphocytes and plasma cells, are seen infiltrating the interstitium (hematoxylin-eosin staining, ×200). (d) Immunohistochemical staining shows mostly CD138-positive plasma cells in the interstitium. (e, f) Immunohistochemical staining shows seven and thirteen IgG4+ and IgG + plasma cells in the same area of serial sections, respectively (Figures 1(e,f)) (indicated by the arrows). So the IgG4+/IgG + plasma cells ratio is calculated to be 53%.

Figure 2.

Changes in renal function during the follow-up, as indicated by the serum creatinine level.