患者男，49岁，因“发热半年余”就诊。患者在当地医院诊断为“干燥综合征”，予泼尼松60 mg/d口服治疗后热退，但泼尼松减量至40 mg/d后再次发热。入院后因发现血培养及便培养示肠炎沙门菌阳性，先后予头孢他啶、头孢曲松、亚胺培南-西司他丁抗感染治疗共4周，但体温仍未控制。患者虽无呼吸系统症状及体征，且胸部高分辨CT未见明显异常，但检查发现动脉血氧分压降低，乳酸脱氢酶及βn 2微球蛋白显著升高，肺功能检查显示弥散功能减低，正电子发射计算机体层显像（PET）/CT见双肺弥漫性代谢增高，最终通过支气管镜下肺活检诊断肺血管内大B细胞淋巴瘤（IVLBCL）。n “,”A 49-year-old male was admitted to Peking Union Medical College Hospital presented with fever for more than half a year. The patient was diagnosed as Sjogren′s syndrome at local hospital. After oral prednisone 60 mg per day was given, the fever alleviated, but recurred after prednisone tapered to 40 mg/d. Both blood culture and stool culture were positive for n Salmonella enteritidis. Antibiotics including ceftazidime, ceftriaxone, cilastatin-imipenem were sequentially administrated for 4 weeks, yet not effective. Although there were not respiratory symptoms or certain abnormalities on high-resolution chest CT, arterial blood gas indicated hypoxemia. Serum lactate dehydrogenase and β2 micro-globulin were elevated, and the lung function test demonstrated significant impairment of diffusion function. Positron emission tomography-computed tomography (PET/CT)scan suggested that high fluorodeoxyglucose uptake was diffusely seen in both lungs. The patient was finally diagnosed as pulmonary intravascular large B-cell lymphoma (IVLBCL) by transbronchial lung biopsy. This case aims to emphasize the differentiation diagnoses of pulmonary intravascular lymphoma from common situations.n