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Abstract IgG4‐related diseases are adverse events that occur after receiving treatment with immune checkpoint inhibitors (ICI). This study reports the first case of IgG4‐related retroperitoneal fibrosis after the administration of chemotherapy with nivolumab and ipilimumab (NI therapy). An 80‐year‐old man developed lower abdominal pain eight months after NI therapy was initiated. Although the primary lesion maintained its reduced size on computed tomography, there was an increase in the soft tissue shadows intensity around the abdominal aorta, bladder, and seminal vesicles, suggesting retroperitoneal fibrosis. Blood tests showed elevated IgG4 levels. Computed tomography‐guided biopsy of the retroperitoneum showed B cell‐dominant lymphocyte infiltration consistent with IgG4‐related retroperitoneal fibrosis and characteristic CD8‐positive lymphocyte infiltration, suggestive of the involvement of cytotoxic T cells. Based on the clinical, imaging, and pathological findings, the patient was diagnosed with IgG4‐related retroperitoneal fibrosis due to ICI. Immunotherapy discontinuation alone did not result in improvement; therefore, steroid therapy was initiated. In clinical practice, IgG4‐related retroperitoneal fibrosis can occur as an immune‐related adverse event when administering anti‐PD‐1 and anti‐CTLA‐4 antibodies for cancer immunotherapy. Early steroid therapy could be effective in controlling this immune‐related adverse event.

Introduction: Diffuse lung cysts occur owing to several diseases; however, diffuse cystic lung metastases are very rare in the case of lung cancer. We report a rare case of diffuse cystic lung metastases from lung adenocarcinoma and reviewed previously reported cases of cystic lung metastases for lung cancer and determined their characteristics. Case Presentation: A 78-year-old Japanese woman with advanced lung adenocarcinoma was positive for the epidermal growth factor receptor gene mutation exon 21 L858R and had been treated with osimertinib. She presented with multiple bilaterally positioned thin-walled lung cysts and pneumothorax. Lung cysts were diagnosed as cystic lung metastases from lung cancer, and carboplatin, pemetrexed, and pembrolizumab were subsequently administered. All cysts markedly decreased in size, and some disappeared. Conclusion: Effective treatment methods for cystic lung metastases from lung cancer have not been reported. To our knowledge, this is the first case of cystic lung metastases that were successfully treated with chemotherapy.

Key message We present the case of a patient who developed a massive right pleural effusion after pelvic surgery, not thoracic surgery. Lymphatic leakage into the abdominal cavity after pelvic surgery can cause massive pleural effusion when complicated with porous diaphragm syndrome.

Eosinophilic pleural effusion is rare, and the cause is often obscure. A 73-year-old man with no relevant medical history presented with exertional dyspnea. Chest imaging revealed left-sided pleural effusion, and pleural fluid examination revealed eosinophilic pleural effusion. Blood tests revealed an increased peripheral blood eosinophil count and elevated Immunoglobulin E levels. Staphylococcus epidermidis was detected in pleural specimens collected via thoracoscopy. Antimicrobial therapy targeting Staphylococcus epidermidis resolved the eosinophilic pleural effusion and elevated peripheral blood eosinophil count. Staphylococcus epidermidis infection may be considered as a cause of eosinophilic pleural effusion when the diagnosis is difficult.

A 60-year-old man treated with valproic acid (VPA) for epilepsy developed atelectasis and respiratory failure after an accidentally aspirated VPA tablet-induced mucus hypersecretion. Following bronchoscopic removal of the aspirated tablet, his respiratory status improved and massive sputum production did not recur. We hypothesized that the aspirated VPA tablet increased the expression of mucin-related genes, thereby increasing mucus production. Our in vitro experiments using a human respiratory epithelial cell line revealed that VPA directly upregulates the airway mucin-related genes. We believe that this is the first case report of aspirated VPA-induced severe atelectasis and respiratory failure, which were successfully treated with the bronchoscopic removal of the VPA tablet.

Introduction: Whole genome sequencing (WGS) of influenza viruses is important for preparing vaccines and coping with newly emerging viruses. However, WGS is difficult to perform using conventional next-generation sequencers in developing countries, where facilities are often inadequate. In this study, we developed a high-throughput WGS method for influenza viruses in clinical specimens with the MinION portable sequencer.Methods: Whole genomes of influenza A and B viruses were amplified by multiplex RT-PCR from 13 clinical specimens collected in Tokyo, Japan. Barcode tags for multiplex MinION sequencing were added with each multiplex RT-PCR amplicon by nested PCR with custom barcoded primers. All barcoded amplicons were mixed and multiplex sequencing using the MinION sequencer with 1D2 sequencing kit. In addition, multiplex RT-PCR amplicons generated from each clinical specimen were sequenced using the Illumina MiSeq platform to validate the performance of MinION sequencer. The accuracy, recall, and precision rates of MinION sequencing were calculated by comparing the results of variant calling in the Illumina MiSeq platform and MinION sequencer.Results: Whole genomes of influenza A and B viruses were successfully amplified by multiplex RT-PCR from 13 clinical samples. We identified 6 samples as influenza type A virus H3N2 subtype and 7 as influenza B virus Yamagata lineage using the Illumina MiSeq platform. The overall accuracy, recall, and precision rates of the MinION sequencer were, respectively 99.95%, 89.41%, and 97.88% from 1D reads and 99.97%, 93.28%, and 99.86% from 1D2 reads.Conclusion: We developed a novel WGS method for influenza A and B viruses. It is necessary to improve read accuracy and analytical tools in order to better utilize the MinION sequencer for real-time monitoring of genetic rearrangements and for evaluation of newly emerging viruses.