IgG4-related lymphadenopathy: A misdiagnosed case report

Rationale: IgG4-related lymphadenopathy (IgG4-RLP), a challenging diagnostic entity within IgG4-related disease (IgG4-RD), often faces delays in treatment due to frequent misdiagnosis. Patient concerns: A 53-year-old male presented with a 4-year history of a right upper arm mass and axillary lymphadenopathy. Initial investigations suggested alternative diagnoses, resulting in a prior misdiagnosis of reactive lymph node hyperplasia. The patient presented with enlarged axillary lymph nodes. Imaging showed cortical thickening, loss of cortico-medullary differentiation, and homogeneous enhancement on CT. Routine lab results were unremarkable, but ultrasound revealed multiple enlarged lymph nodes. Diagnoses: A multidisciplinary approach, including core needle biopsy and retrospective analysis, confirmed systemic IgG4-RLP. The diagnosis included a unique “checkerboard-like” fibrosis pattern in a prior specimen, and elevated IgG4 levels. Interventions: The patient was treated with methylprednisolone. Outcomes: The patient experienced significant symptom relief, correlating with a decrease in serum IgG4 levels, after initiating steroid treatment, at a 2-week follow-up. Lessons: Diagnosing IgG4-RLP is challenging, especially when encountering atypical histological patterns such as “checkerboard-like” fibrosis. Therefore, unexplained lymphadenopathy characterized by increased plasma cells should prompt high suspicion for IgG4-RLP. Prompt recognition through integrated clinical and laboratory findings is crucial to prevent misdiagnosis and ensure timely intervention.