Severe reversible interstitial pneumonitis induced by low dose methotrexate: report of a case and review of the literature.

A patient treated with 7.5 mg methotrexate/week (MTX) for rheumatoid arthritis (total dose 300 mg) developed high fever, dry cough and progressive dyspnea and hypoxemia due to a severe interstitial pneumonitis. MTX was discontinued and an infectious etiology was ruled out by cultures, serology and lung biopsy. Corticosteroids administered intravenously in high dose led to a dramatic improvement and a complete amelioration of all symptoms and signs. Pulmonary toxicity is a rare adverse effect of low dose MTX therapy and a review of the literature reveals 6 additional cases. Since MTX induced pneumonitis is a potentially fatal, yet completely reversible, disease, attention should be paid to even mild early respiratory symptoms in patients treated with low dose MTX and patient monitoring should include pulmonary function tests.