Interstitial Lung Disease in a Woman with Rheumatoid Arthritis Treated with Denosumab: A Case Report.

The present report describes the case of an 84-year-old female Japanese patient with rheumatoid arthritis (RA) who experienced exacerbation of interstitial lung disease (ILD) after denosumab (Dmab) treatment. The onset of RA occurred in 2008, and the patient had been treated with intravenous or subcutaneous injection of tocilizumab (TCZ) since 2009. In July 2013, she experienced a lumbar vertebral fracture and began treatment with 60-mg Dmab injection every 6 months in January 2014. The patient had a history of mild ILD and was evaluated for ILD by chest computed tomography (CT) imaging prior to the start of Dmab use. The vertebral fracture did not recur after the initiation of Dmab treatment, and her osteoporosis was successfully treated. However, she expressed a concern of exacerbations of cough and respiratory discomfort that had occurred since September 2019. The chest CT image in November 2015 showed minor ILD progression, whereas the image in September 2019 showed severe exacerbation of ILD. To treat this exacerbation, 10 mg of methylprednisolone (mPSL) and 2.5 mg of tacrolimus (TAC) were administered, and Dmab was discontinued. The patient was subsequently switched to oral bisphosphonate. The patient's respiratory discomfort and the finding of interstitial lung lesion in CT imaging improved after Dmab discontinuation. This case showed that exacerbation of ILD may occur after Dmab treatment, and physicians should consider the risks of Dmab-related ILD in patients with RA complicated by ILD.