Acute tubulointerstitial nephritis with severe renal impairment associated with multisystem IgG4-related disease

Abstract The IgG4-related disease has a wide clinical spectrum where multiple organs can be affected, and the diagnosis depends on typical histopathological findings and an elevated IgG4 expression in plasma cells in the affected tissue. We describe the clinical presentation and evolution of a patient with acute tubulointerstitial nephritis, severe kidney failure and systemic manifestations such as lymphadenomegaly and chronic pancreatitis. The diagnosis was confirmed by the clinical picture and kidney and lymph node histopathology, in which immunohistochemistry of the lymphoid tissue showed policlonality and increased expression of IgG4, with a IgG4/total IgG ratio > 80%. The patient was treated with prednisone at a dose of 60 mg/day, followed by mycophenolate mofetil, and showed clinical and renal function improvement at 6 months of follow-up. The high index of suspicion of IgG4-related disease with multisystem involvement and the early treatment of this condition are essential to improve the prognosis of affected patients.