A case of IgG4-related disease seemingly presenting as a T-cell lymphoma

IgG4-related disease (IgG4-RD) is an immune-mediated disorder hallmarked with lymphoplasmacytic tissues infiltrated with abundant IgG4-positive plasma cells, which has various clinical features and easily to be misdiagnosed. Here, we described a case with symptoms of body weight loss and multiple lymph node enlargements in a patient’s groin, axilla, mediastinum, and retroperitoneum at the first admission. Both F-fluorodeoxyglucose (FDG)-position emission tomography (PET) and lymph node biopsies supported the possible diagnosis of this case as a T-cell lymphoma, but no TCR gene rearrangement observed. Further examinations showed that serum IgG4 level of the patient was elevated and large amount of IgG4+ plasmocyte infiltration was detected in the involved lymph nodes, indicating this case as a possible IgG4-RD. However, the possibility of this disease as a T-cell lymphoma still could not be excluded. Tentatively, the patient was first treated as IgG4-RD with oral prednisone combined with methotrexate to avoid the unnecessary side effect of chemotherapy and economy burden. After three weeks treatment, the serum IgG4 level of the patient is evidently decreased and the enlarged lymph nodes disappeared as well. Eventually, we characterized this case as an atypical IgG4-related lymphadenopathy with 20 months’ follow-up.