Abstract
The patient, a 70-year-old woman with diffuse large B-cell lymphoma (DLBCL), developed haemorrhagic cystitis associated with the BK virus (BKV) and adenovirus type 11. Moreover, chest computed tomography showed ground-glass opacity (GGO) in the bilateral upper lobe, and we performed bronchoalveolar lavage (BAL). The BKV DNA load was elevated not only in blood but also in BAL fluid (BALF), leading to the diagnosis of BKV pneumonia. After administering cidofovir, the respiratory symptoms and GGO abated. Therefore, detection of BKV DNA in BALF is useful for diagnosing BKV pneumonia. The patient with DLBCL developed BKV pneumonia. We performed BAL, and BKV DNA load was elevated on BALF. The detection of BKV DNA in BALF is useful for diagnosing BKV pneumonia.