BI38 Methotrexate-associated lymphoma in atopic dermatitis: two case reports

Abstract

Methotrexate (MTX) is widely used off-label for moderate-to-­severe atopic dermatitis (AD), but its potential to induce lymphoproliferative disorders (LPDs) is best recognized in other autoimmune diseases. MTX-associated LPDs occur predominantly in patients with rheumatoid arthritis treated with MTX and are reported less commonly in psoriasis and dermatomyositis. Approximately 75–85% of cases of MTX-induced LPD occur in rheumatoid arthritis, and B-cell lineage is most frequent, with occasional reports from patients with psoriasis. Cases in AD have not been clearly documented in the indexed literature to date. We present two male patients with AD on long-term low-dose MTX who developed histologically confirmed lymphoma. Case 1: a 51-year-old man with lifelong AD treated with MTX for 2 years presented with a right axillary mass. Biopsy confirmed Hodgkin lymphoma (HL) and MTX was discontinued. Persistent disease required R-CHOP chemotherapy, with good metabolic response. Two years later he developed para-aortic and coeliac lymphadenopathy; biopsy confirmed relapse of Hodgkin lymphoma. He received R-GDP followed by BEAM autologous stem cell transplant and remains in remission. Narrowband ultraviolet B phototherapy provided effective control of his AD during this period. Case 2: a 52-year-old man with AD on MTX for 4 years presented with fever and cervical lymphadenopathy. Initial biopsy was suggestive of Hodgkin lymphoma, but further immunophenotyping revised the diagnosis to peripheral T-cell lymphoma, not otherwise specified. He received urgent R-CHOP therapy, achieved an excellent response, had residual nodes treated with radiotherapy, and underwent BEAM autologous stem cell transplant. These cases may represent the first reported instances of MTX-associated lymphoma in the context of AD, expanding the spectrum of MTX-induced LPD outside established autoimmune indications. They highlight the need for clinical vigilance for unexplained lymphadenopathy in patients with AD on systemic immunosuppression and underscore the importance of histological diagnosis, prompt MTX cessation and appropriate oncological management.