Severe stomatitis caused by misuse of methotrexate in an elderly patient with chronic rheumatoid arthritis

Methotrexate (MTX) is an antifolate that has been used as a chemotherapeutic agent for the treatment of neoplasm, such as leukemia and osteosarcoma. Moreover, MTX is also commonly used for treatment of chronic rheumatoid arthritis (RA). Here, we report a case of severe stomatitis in a patient with RA, which was caused by misuse of MTX. An 83-year-old female patient visited our department with the chief complaint of oral mucosal pain, accompanied by extreme fatigue. Severe stomatitis lesions were observed throughout her oral mucosa. Moreover, blood examination revealed pancytopenia. The patient reported a history of RA, and had been prescribed MTX since 2004. Although 6 mg MTX should be used twice per week, the patient mistakenly used MTX every day following her last consultation, for a period of 1 month. These findings led to a diagnosis of severe stomatitis, pancytopenia, and sepsis, all induced by misuse of MTX. Ultimately, she was treated with blood transfusion, antibiotics, and intravenous hyper alimentation, as well as administration of granulocyte colony-stimulating factor. MTX for the treatment of RA should be carefully managed to limit the risk of its misuse, especially in elderly patients, because of the severity and potential lethality of symptoms.