Nivolumab-induced Acute Fibrinous and Organizing Pneumonia (AFOP).

Although nivolumab is known to cause immune-related interstitial lung diseases (ILD), the detailed characteristics of ILD are still not fully understood. A 68-year-old man was treated with nivolumab because of unresectable sinonasal melanoma, he achieved a complete response soon after the initiation of the therapy and a complete response was thereafter maintained for 30 weeks until the patient experienced dyspnea of subacute onset. CT images revealed patchy infiltrates and ground-glass opacifications. The bronchoalveolar lavage fluid (BALF) contained elevated percentages of lymphocytes (53%) and neutrophils (30%). A transbronchial lung biopsy revealed intraalveolar fibrin balls without hyaline membranes, which was considered to be consistent with the pattern of acute fibrinous and organizing pneumonia (AFOP). This is the first report of AFOP induced by nivolumab.