Multi-organ IgG4-related disease: Demystifying the diagnostic enigma.

IgG4-related disease (IgG4-RD) is a multisystemic mass forming immune-mediated disease entity, commonly creating confusion and diagnostic challenges. We present a case of a 25-year-old female who presented with bilateral orbital masses, lymphadenopathy, paraspinal and renal masses, which clinicoradiologically simulated lymphoma. The lymph node biopsy revealed interfollicular sheets of plasma cells creating confusion with Castleman's disease and marginal zone lymphoma. The orbital biopsy revealed ductular destruction, periductular plasma cells, and fibrosis, mimicking Sjogren's syndrome and Castleman's disease. However, the correlation of the clinical features with histopathological findings, IgG4 immunopositivity, and serum studies helped in clinching the diagnosis. This case presents an uncommon combination of clinical features infrequently reported in literature. Furthermore, and more importantly, it highlights the need to keep a differential of IgG4-RD in mind, to aid early and correct treatment of the disease.