Case Presentation: A 66-year-old man with history of hypertension, gastroesophageal reflux disease, and hyperlipidemia presented with jaundice and one week of diarrhea with occasional hematochezia. In addition, he noted dark urine, decreased PO intake and appetite.
On exam, he was jaundiced with scleral icterus. Lab work revealed acute kidney injury with initial creatinine level of 5.08 mg/dL, as well as mixed hepatocellular and cholestatic liver injury. Further workup showed paraproteinemia with elevated total protein and low albumin, elevated IgG (6282) with IgG4 level of 1960, and low levels of C3 and C4. Serum protein electrophoresis was significant for IgG kappa and lambda monoclonal protein.
A renal biopsy was obtained. The initial biopsy showed plasma-cell rich interstitial infiltrate with no tubular casts and normal glomeruli. The patient was started on high dose solumedrol the day of renal biopsy. He was noted to have improvement in kidney and liver function with initiation of steroids. Final pathology demonstrated severe tubulointerstitial inflammation with overwhelming plasma cell infiltrate and polyclonal IgG4, confirming a diagnosis of IgG4-related tubulointerstitial nephritis. He underwent liver biopsy to evaluate for autoimmune hepatitis, which showed predominate cholestasis and portal based inflammation without classic features of autoimmune hepatitis or IgG4 related disease.
His creatinine and liver function tests continued to trend down after initiating solumedrol and subsequent prednisone therapy. He was discharged to home with a serum creatinine level of 2 mg/dL with improved diarrhea and jaundice. Steroid therapy was tapered outpatient. On follow up one month after discharge he was noted to have significantly improved creatinine of 1.44 mg/dL, IgG4 level of 262, and normalized LFTs, C3, and C4 levels.
Discussion: IgG4-related disease is a disorder characterized by multi-organ dysfunction with elevated serum IgG4 levels and dense infiltrates of IgG4 in the organs. The disease is generally known for extra-renal manifestations including pancreatitis; however, renal involvement is one of the leading manifestations of IgG4-related disease. It has been estimated 15-25% of patients with IgG4-related disease also have tubulointerstitial nephritis. In most patients, there are concomitant extra-renal lesions noted at presentation, including pancreatitis, sclerosing cholangitis, or lymphadenopathy. The disease is more common in middle aged or elderly men. Labs are significant for hypergammaglobulinemia and hypocomplementemia, and diagnosis should be confirmed with renal biopsy. Treatment includes steroid therapy with some case series showing up to 89% response rate.
Conclusions: Hospitalists should consider IgG4-related tubulointerstitial disease in the differential of patients presenting with AKI, especially in older men with extra-renal manifestations such as pancreatitis. Early recognition is paramount, as the disease is strongly responsive to steroids.