IgG₄-related lymphadenopathy masquerading as Hodgkin lymphoma: lessons from a pathologist's desk

IgG₄-related disease (IgG₄-RD) is a systemic fibroinflammatory disorder affecting multiple organ systems. The awareness of this disease has tremendously increased over the last decade leading to effective treatment and decreased morbidity to the patients. Histopathology plays an important role in the diagnosis of IgG₄-RD, and definite histologic criteria are proposed in clinically suspected patients. We report a patient with multiple organ system involvements of the salivary gland, lymph node and kidney. IgG₄-related lymphadenopathy (IgG₄-RL) in this patient was misdiagnosed as nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL). Refractoriness to treatment for NLPHL and subsequent manifestations of renal involvement lead us to the correct diagnosis of this potentially treatable condition. IgG₄-RL can mimic reactive proliferation as well as lymphomas. We report the clinical presentation and discuss the problems faced by pathologists in diagnosing IgG₄-RL. We believe that awareness of this rare presentation will enhance the knowledge in diagnosing IgG₄-RD.