[Two cases of acetaminophen-induced pneumonitis]

This paper deals with two patients with acetaminophen-induced pneumonitis. A 64-year-old woman suffered from mastitis while being treated by corticosteroid therapy for phemphigoid. She was administered antibiotics and acetaminophen. However, her fever continued and she subsequently developed dyspnea and interstitial pneumonia. The other patient, a 70-year-old woman, was treated with corticosteroid for lower motor neuron disease. Anti-GM1-IgM antibodies were positive in her serum. She developed wet cough and mild fever. During treatment with antibiotics and acetaminophen, her illness was complicated by dyspnea and interstital pneumonia. As a result of histological findings of transbronchial lung biopsy specimens showing interstitial infiltration of mononuclear cells, as well as clinical courses in which cessation of acetaminophen directly lead to the improvement of interstitial pneumonia, both patients were diagnosed to have acetaminophen-induced pneumonitis. The peumonitis responded well to steroid therapy. In vitro culture of peripheral lymphocytes showed stimulated proliferation by acetaminophen in both patients. These findings suggest that allergic mechanism was involved in the pathogenesis of the pneumonitis. Underlying immunological disorders may have enhanced the occurrence. Although acetaminophen is one of the most popular drugs because of a very low incidence of side effects, this drug should be applied carefully, especially with patients who have such immunological disorders.