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.
Highlights
IgG4-related acute tubulointerstitial nephritis is a type of autoimmune-mediated interstitial nephritis
The modified C-reactive protein (mCRP) monomers undergo conformational rearrangements to form isomers with distinct antigenic and physiochemical characteristics. mCRP is considered as the tissue and/or cellular form of acute reactive protein [5]. mCRP plays a role in the safe clearance of apoptotic material, and provides protection against unwanted complement activation in the fluid phase [6]
It was demonstrated that mCRP autoantibodies are highly prevalent in patients with tubulointerstitial nephritis and uveitis (TINU); further, mCRP autoantibodies are associated with disease activity and treatment effectiveness in patients with TINU [7]
Summary
Acute interstitial nephritis (AIN) is one of the frequent causes of acute renal failure, and AIN accounts for 15–27% of all renal lesions [1]. In two large-scale studies on a series of patients with AIN, all the patients presented with acute renal failure [2,3]. According to the main causative factors, AIN can be classified into three types: drug induced, infection related, and autoimmune mediated. Autoimmune-mediated AIN accounts for 15–25% of all AIN cases [4]. Some examples of autoimmune-mediated AIN are Sjogren’s syndrome, lupus nephritis, tubulointerstitial nephritis and uveitis (TINU), and IgG4-related tubulointerstitial nephritis (TIN)
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