Clinical characteristics of drug-induced interstitial pneumonia in Japan

Japan has a higher incidence of drug-induced interstitial pneumonia (IP) than other countries. Understanding the clinical characteristics of drug-induced IP in Japan will facilitate accurate diagnosis of the disease. The aim of this study was to analyze and report the clinical characteristics of drug-induced IP in Japan.

We analyzed the characteristics of drug-induced IP diagnosed between 2009 and 2022 in Japan. Case data were collated with the cooperation of pharmaceutical companies, as requested by the Ministry of Health, Labour and Welfare.

We identified 285 patients with drug-induced IP diagnosed in medical institutions. The most common causative drugs identified were antineoplastic agents (56.1 %). Common subjective symptoms included dyspnea (158 patients [55.4 %]), cough (132 patients [46.3 %]), and fever (115 patients [40.4 %]). In addition, 177 patients (73.1 % of those measured) showed elevated serum KL-6, SP-D, or SP-A levels. Approximately 60 % of the patients developed IP within 90 days from the initiation of drug therapy, whereas 15 % developed the disease after >1 year. Regarding imaging findings, 249 patients (87.4 %) showed bilateral shadows. Corticosteroid therapy was administered to 222 patients (77.9 %). The treatment outcomes of drug-induced IP in Japan were favorable, with improvement observed in 273 patients (95.8 %).

Dyspnea, cough, and fever after administration of a drug; elevated serum KL-6, SP-D, and SP-A levels; and bilateral shadows were identified as clinical features of drug-induced IP in Japan. Drug-induced IP should be considered a differential diagnosis even if the patient started using the causative drug long ago.