Bowel perforation due to methotrexate therapeutic error: an insidious adverse reaction.

OBJECTIVE: Methotrexate (MTX) is widely used in the treatment of rheumatic and non-rheumatic disorders. Severe adverse effects are often associated with therapeutic errors, such as daily intake rather than weekly intake. Among them, the risk of bowel perforation is extremely rare (0.1%). We describe a case of bowel perforation, occurred following daily intake of MTX. CASE REPORT: A 68-year-old man was prescribed to take MTX 7,5 mg orally once a week, while waiting for switch to abatacept for a recent reactivation of rheumatoid arthritis. After 10 days he started having pharyngodynia, hematochezia and general malaise. At medical examination he presented oral and nasal mucositis; moreover, blood exams showed thrombocytopenia. The anamnesis revealed that he had been taken the prescribed dosage of MTX daily, instead of weekly. Therapy with Lederfolin 1000 mg (mg/m²/die) and urine alkalinization started. After 7 days of hospitalization, there was an abrupt worsening of clinical conditions and an emergency CT scan revealed millimetric gas bubbles indicating bowel perforation. The patient underwent an emergency exploratory laparotomy that resulted in peritoneal toilette and sigma resections. Anatomopathological findings were suggestive of MTX poisoning. CONCLUSIONS: The patient was discharged on the 17th day in good clinical condition. [ABSTRACT FROM AUTHOR]