Progressive interstitial lung disease from prolonged methotrexate therapy.

Progressive interstitial fibrosis with roentgenographic honeycombing developed in the case of a psoriatic patient who had been on a regimen of methotrexate for 18 years. Examination revealed a combined restrictive and obstructive defect in pulmonary mechanics and severe compromise of gas transfer across the pulmonary alveolar-capillary membrane. Improvement in the level of arterial blood gases and pulmonary diffusing capacity occurred after discontinuation of methotrexate therapy. Interstitial fibrosis of the lung is a potential complication of methotrexate therapy for psoriasis.