Nerandomilast-Associated Pneumonitis With a Positive Rechallenge: A Case Report.

Nerandomilast is an oral preferential phosphodiesterase 4B inhibitor that slows the decline in forced vital capacity in idiopathic pulmonary fibrosis and progressive pulmonary fibrosis. Nerandomilast-associated pneumonitis has not previously been reported. A 33-year-old woman with advanced unclassifiable idiopathic interstitial pneumonia developed fever, dyspnoea, hypoxaemia and new bilateral consolidations and ground-glass opacities 9 days after starting nerandomilast. The drug was withdrawn, and her clinical, inflammatory and radiological findings improved during antimicrobial and corticosteroid treatment. Nerandomilast was subsequently restarted at a reduced dose. The following day, symptoms, inflammatory markers and pulmonary opacities worsened and improved again after drug withdrawal. Bronchoalveolar lavage and lung biopsy were not performed because severe chronic hypercapnia made invasive procedures unsafe. The temporal association and positive rechallenge strongly supported nerandomilast-associated pneumonitis. Clinicians should consider drug-induced pneumonitis when new pulmonary infiltrates develop after starting an antifibrotic agent.