Brachial Plexus Neuropathy Induced By Methotrexate-Associated Lymphoproliferative Disorder In A Patient With Rheumatoid Arthritis

We present a case of 74-year-old female patient with rheumatoid arthritis with left upper limb movement disorder who was diagnosed with brachial plexus neuropathy induced by methotrexate-associated lymphoproliferative disorder (MTX-LPD). Nerve hypertrophy and contrast effects were observed at the left brachial plexus and the more distal peripheral nerves on MRI. An attenuated image at the left axillary lymph node was observed on FDG-PET. A biopsy sample from the same node revealed diffuse large B-cell lymphoma. The symptoms improved in 1 month due to cessation of methotrexate. In patients taking methotrexate with neurological abnormalities, MTX-LPD should be considered in the differential diagnosis.