Lung adenocarcinoma misdiagnosed as IgG4-related lung disease: A case report and literature review.

IgG4-related disease (IgG4-RD) is a recently recognized disorder characterized by elevated serum IgG4 levels and infiltration of IgG4 positive blood cells in the affected organs. However, other conditions like malignancy as well as connective tissue diseases, may show similar findings. A 56-year-old male patient visited Second Xiangya Hospital, Central South University for recurrent fever and chest pain for more than 1 month. Preliminary tests diagnosed as IgG4-related lung disease (IgG4-RLD). However, the improvement of symptoms was absent after the treatment with methylprednisolone. The patient underwent the second biopsy and the result eventually demonstrated lung adenocarcinoma. The role of IgG4 in the pathogenesis or prognosis for lung adenocarcinoma remains unclear. Therefore, a thorough evaluation of symptoms, test of specific serum markers and eventually pathological confirmation are required to avoid misdiagnosis.