When weekly becomes daily: mucocutaneous ulceration and pancytopenia after a methotrexate dosing error

The methotrexate is prescribed as a single dose per week for rheumatoid arthritis. It is dangerous if patient consumes the medication daily by mistake. We present a case of a 64-year-old female with diabetes with newly diagnosed rheumatoid arthritis who consumed 10 mg of methotrexate daily for five to six days instead of once weekly. In a few days the patient developed oral painful ulcers, difficulty in swallowing, bilateral leg ulcers with peeling of skin and fever. Blood tests showed pancytopenia, leucocytes were 1.75×10³/µl, platelets were 50×10³/µl. The methotrexate was stopped and gave 15 mg of intravenous folinic acid every sixth hourly for five days. Her platelets increased within four days. The oral and leg ulcers began to heal by the end of the first week. Skin ulcers are very uncommon manifestation of this toxicity - but clear instructions for weekly dosing can prevent this medication error.