Immune-Related Encephalitis in a Patient With Pleural Mesothelioma: Case Report

Our plain-English summary of Immune-Related Encephalitis in a Patient With Pleural Mesothelioma: Case Report, by F. Onishi, N. Hara, M. Ota, et al (Respirology Case Reports, 2026).

The study

• Authors: F. Onishi, N. Hara, M. Ota, K. Onishi, Y. Fujioka, H. Tanaka, N. Fujimoto
• Journal: Respirology Case Reports
• Published: 2026;14(9):e70748
• Read it: PubMed · Publisher · Free full text

Abstract

A 69-year-old man who was a former plumber with a history of occupational asbestos exposure was diagnosed with unresectable pleural mesothelioma. Six months after initiation of combination therapy with ipilimumab and nivolumab, he presented with an altered level of consciousness and extrapyramidal symptoms and was diagnosed with immune-related encephalitis. Although high-dose corticosteroid therapy and intravenous immunoglobulin led to partial improvement in his level of consciousness, the response was limited. Immune-related encephalitis is rare, especially in association with pleural mesothelioma. Optimal management of the condition needs to be established.

© 2026 The Author(s). Respirology Case Reports published by John Wiley & Sons Australia, Ltd on behalf of The Asian Pacific Society of Respirology.

In plain English

This case report described one patient at Okayama Rosai Hospital in Japan: a 69-year-old former plumber with a history of occupational asbestos exposure, diagnosed with pleural mesothelioma that could not be removed surgically. No asbestos fiber type was named. The patient received two immune checkpoint inhibitor drugs, ipilimumab and nivolumab. Six months later, at the fourth course, the patient was brought to hospital with an altered level of consciousness, memory and orientation problems, and tremors suggestive of extrapyramidal symptoms. Spinal fluid showed a mildly raised protein level (61 mg/dL), and autoantibody tests were negative. Because the brain MRI abnormality was only on the left side, the authors considered immune-related encephalitis probable rather than definite. High-dose corticosteroids and intravenous immunoglobulin brought partial improvement in consciousness, but the response was limited. The patient died 21 months after the mesothelioma diagnosis and 15 months after the encephalitis began. The authors concluded that this condition is rare and that its optimal management needs to be established.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case report (one patient)
• Who was studied: One 69-year-old man, a former plumber, with unresectable pleural mesothelioma, treated at Okayama Rosai Hospital, Japan. Comorbidities were hypertension and rheumatoid arthritis.
• Exposure: Occupational asbestos exposure as a plumber. The fiber type was not stated. The encephalitis followed treatment with ipilimumab (1 mg/kg every 6 weeks) plus nivolumab (360 mg/body every 3 weeks).
• Main results:
  • Pleural mesothelioma was diagnosed from a right pleural effusion by cytology, including cell block analysis of BAP1.
  • Six months after treatment began, at the fourth course, the patient had an altered level of consciousness and cognitive disturbance.
  • Memory and orientation were impaired, and tremors of the arms and legs suggestive of extrapyramidal symptoms were observed.
  • The patient's cerebrospinal fluid showed no significant pleocytosis (cell count 5/μL) and a mildly raised protein level of 61 mg/dL.
  • Autoantibody tests, including anti-Hu, anti-Yo, anti-Ri and a paraneoplastic panel including anti-Ma2, were negative.
  • Because the MRI signal abnormality was seen only in the left basal temporal lobe, the authors considered the diagnosis of immune-related encephalitis probable rather than definite.
  • High-dose corticosteroids and intravenous immunoglobulin partly improved the patient's level of consciousness, but the response was limited.
  • The patient died 21 months after the mesothelioma diagnosis and 15 months after the onset of encephalitis.
• The authors' conclusion: The authors concluded that immune-related encephalitis is rare, has nonspecific symptoms and often minimal abnormal test findings, and that its optimal management should be established.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Asbestos Exposure, Unresectable Pleural Mesothelioma, Ipilimumab (Yervoy), Nivolumab (Opdivo).

Related studies

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• Anti-Ma2-Associated Limbic Encephalitis after Termination of Immune Checkpoint Inhibitor Therapy for Malignant Pleural Mesothelioma — R. Hashimoto, E. Tanabe, et al. (2021)
• Case Report: Immune checkpoint inhibitor-triggered anti-Ma2 paraneoplastic encephalitis in sarcomatoid pleural mesothelioma: a fatal case — I.N. Okten, T. Baydaş (2026)
• Paraneoplastic Brachial Amyotrophic Diplegia and Encephalitis With Ma2-IgG During Immune Checkpoint Inhibitor Use for Mesothelioma: A Case Report — S.P. Uysal, S. Badihian, et al. (2026)
• Fatal Anti-Ma2 Encephalitis Related to Treatment of Malignant Pleural Mesothelioma With a Combination of Anti-Programmed Death 1 and Anti-Cytotoxic T-Lymphocyte Associated Protein 4 Antibodies — P. Du Rusquec, A. Peyre, et al. (2019)
• Thrombocytopenia as an Immune-Related Adverse Event in Malignant Pleural Mesothelioma: A Case Report — T. Tanaka, S. Asakura, et al. (2022)

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