Fevers, Sweats, Weight Loss, Oh My! When IgG4 Related Disease Comes Knocking. . .

Immunoglobulin G4-related systemic disease (IgG4-RSD) is a fibro-inflammatory immune condition characterized by IgG4 positive plasma cells, fibrosis, and frequently elevated serum IgG4 level. Akin to sarcoidosis, IgG4-RSD is a systemic disease with diverse organ manifestations linked by common histopathologic features. IgG4-RSD typically presents sub acutely without significant constitutional symptoms or fever. Hepatic Inflammatory pseudotumor (HIP) is a rare manifestation of IgG4-RSD composed of dense lymphoplasmacytic infiltrate and extensive fibrosis. We present an older Asian male who presented with acute onset of fever and weight loss found to have IgG4-RSD complicated by a HIP and concomitant MSSA abscess.