A Rare Case of Methotrexate-Associated Lymphoproliferative Disease in the Orbit.

An 80-year-old Caucasian female with a history of rheumatoid arthritis presented with a 6-month history of progressive right upper eyelid ptosis, edema, erythema, and pain. MRI demonstrated a superior orbital mass. An incisional biopsy was performed, and pathologic analysis revealed an atypical lymphoid infiltrate, co-expressing both B and T-cell markers, with a low proliferation rate. Flow cytometry and IgH rearrangement study did not demonstrate any B- or T-cell monoclonal proliferation. Based on these findings, she was diagnosed with an iatrogenic immunodeficiency-associated lymphoproliferative disorder. Discontinuation of methotrexate resulted in the complete resolution of her symptoms, and she remains in remission 18 months later. Given the increased risk of lymphoproliferative disease in patients with rheumatoid arthritis, careful evaluation and close monitoring upon immunosuppressive medication withdrawal is necessary to confirm the diagnosis.