IgG4-related disease: A common manifestation in an uncommon genus

Background: IgG4-related disease (IgG4-RD) is a recently described clinicopathological condition with a wide range of clinical manifestations: a dense lymphoplasmacytic infiltrate rich in IgG4positive plasma cells, fibrosis arranged in a storiform pattern, obliterative phlebitis, and, elevated serum IgG4 concentrations. Treatment involves corticosteroids and rituximab for the most severe cases. Case Presentation: Here we present two cases, two white females (ages 26 years and 50 years) IgG 4-RD with low back, flank pain, and retroperitoneal mass, with a compressive effect on the kidney and ureter and causing hydronephrosis. Biopsy of mass revealed infiltrates with IgG4 plasma cells, consistent with the diagnosis of IgG4 disease. The patients were treated with steroids, and rituximab showed significant improvement. Conclusion: Retroperitoneal fibrosis (RPF), a rarest cause of back pain in young adults, should be suspected in patients with back pain, renal dysfunction, and other associated symptoms. It is important to identify this particular cause as it is treatable and may be easily missed. The workup includes kidney function assessment and abdominal imaging using computet tomography (CT) or magnetic resonance imaging (MRI). Biopsy of the mass helps identify malignancy.