{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,16]],"date-time":"2026-06-16T19:52:53Z","timestamp":1781639573502,"version":"3.54.5"},"reference-count":10,"publisher":"Springer Science and Business Media LLC","issue":"2","license":[{"start":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T00:00:00Z","timestamp":1772236800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T00:00:00Z","timestamp":1772236800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Cerebellum"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Progressive multifocal leukoencephalopathy (PML) is a rare but devastating demyelinating disease usually seen in immunocompromised patients. We describe a 52-year-old man with pulmonary sarcoidosis, who presented with progressive ataxia, dysarthria, and unsteadiness of gait. He was not on immunosuppressive therapy at the onset of balance problems. Initial imaging showed increased signal in the cerebellar peduncles suggestive of cerebellar variant of multiple system atrophy (MSA-C). Cerebellar biopsy revealed PML. The patient\u2019s condition deteriorated until pembrolizumab, a PD-1 checkpoint inhibitor, was commenced. He subsequently showed slow but sustained clinical improvement, supported by radiological (reduced enhancement) and spectroscopic evidence (increased N-Acetyl Aspartate to Creatine ratio), and he remains stable four years later. This case highlights the diagnostic challenge of PML in the absence of ongoing immunosuppression, and illustrates the potential role of pembrolizumab as a disease-modifying therapy. Early recognition and consideration of immunotherapy may be critical to improving outcomes in this otherwise often fatal condition.<\/jats:p>","DOI":"10.1007\/s12311-026-01973-9","type":"journal-article","created":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:32:45Z","timestamp":1772253165000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Pembrolizumab-Responsive Cerebellar PML in Untreated Sarcoidosis: A Case Report"],"prefix":"10.1007","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-6579-0900","authenticated-orcid":false,"given":"Ella","family":"Jack-kee","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Natasha","family":"Hoyle","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2542-8954","authenticated-orcid":false,"given":"Marios","family":"Hadjivassiliou","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,2,28]]},"reference":[{"issue":"1","key":"1973_CR1","doi-asserted-by":"publisher","first-page":"fcab266","DOI":"10.1093\/braincomms\/fcab266","volume":"4","author":"SC Rosenkranz","year":"2021","unstructured":"Rosenkranz SC, H\u00e4u\u00dfler V, Kolster M, Willing A, Matschke J, R\u00f6cken C, et al. Treating sarcoidosis-associated progressive multifocal leukoencephalopathy with infliximab. Brain Commun. 2021;4(1):fcab266. https:\/\/doi.org\/10.1093\/braincomms\/fcab266.","journal-title":"Brain Commun"},{"key":"1973_CR2","doi-asserted-by":"publisher","first-page":"e01514","DOI":"10.1016\/j.idcr.2022.e01514","volume":"28","author":"T Chatterjee","year":"2022","unstructured":"Chatterjee T, Roy M, Lin RC, Almoujahed MO, Ahmad S. Pembrolizumab for the treatment of progressive multifocal leukoencephalopathy (PML) in a patient with AIDS: a case report and literature review. IDCases. 2022;28:e01514. . https:\/\/doi.org\/10.1016\/j.idcr.2022.e01514","journal-title":"IDCases"},{"issue":"15","key":"1973_CR3","doi-asserted-by":"publisher","first-page":"1307","DOI":"10.1212\/WNL.0000000000000318","volume":"82","author":"Y Jamilloux","year":"2014","unstructured":"Jamilloux Y, N\u00e9el A, Lecouffe-Desprets M, F\u00e8vre A, Kerever S, Guillon B, et al. Progressive multifocal leukoencephalopathy in patients with sarcoidosis. Neurology. 2014;82(15):1307\u201313. . https:\/\/doi.org\/10.1212\/WNL.0000000000000318","journal-title":"Neurology"},{"issue":"6","key":"1973_CR4","doi-asserted-by":"publisher","first-page":"624","DOI":"10.1001\/jamaneurol.2023.0841","volume":"80","author":"CRS McEntire","year":"2023","unstructured":"McEntire CRS, Fletcher A, Toledano M, Epstein S, White E, Tan CS, et al. Characteristics of progressive multifocal leukoencephalopathy associated with sarcoidosis without therapeutic immune suppression. JAMA Neurol. 2023;80(6):624\u201333. https:\/\/doi.org\/10.1001\/jamaneurol.2023.0841.","journal-title":"JAMA Neurol"},{"key":"1973_CR5","doi-asserted-by":"publisher","unstructured":"\u00d6zt\u00fcrk G, Tekeli E\u0130, Erdo\u011fan S, G\u00fcng\u00f6r H, G\u00fcltekin M, \u015eahin T. Progressive multifocal leukoencephalopathy in sarcoidosis successfully treated with pembrolizumab. J Neurovirol 2024;30(3):441\u20134. https:\/\/doi.org\/10.1007\/s13365-024-01227-6","DOI":"10.1007\/s13365-024-01227-6"},{"key":"1973_CR6","doi-asserted-by":"publisher","first-page":"175628642199368","DOI":"10.1177\/1756286421993684","volume":"14","author":"N M\u00f6hn","year":"2021","unstructured":"M\u00f6hn N, Wattjes MP, Adams O, Nay S, Tkachenko D, Salge F, et al. PD\u20131-inhibitor pembrolizumab for treatment of progressive multifocal leukoencephalopathy. Ther Adv Neurol Disord. 2021;14:1756286421993684. . https:\/\/doi.org\/10.1177\/1756286421993684","journal-title":"Ther Adv Neurol Disord"},{"issue":"17","key":"1973_CR7","doi-asserted-by":"publisher","first-page":"1597","DOI":"10.1056\/NEJMoa1815039","volume":"380","author":"I Cortese","year":"2019","unstructured":"Cortese I, Muranski P, Enose-Akahata Y, Ha SK, Smith B, Monaco M, et al. Pembrolizumab treatment for progressive multifocal leukoencephalopathy. N Engl J Med. 2019;380(17):1597\u2013605. . https:\/\/doi.org\/10.1056\/NEJMoa1815039","journal-title":"N Engl J Med"},{"key":"1973_CR8","doi-asserted-by":"publisher","first-page":"186","DOI":"10.1016\/j.clineuro.2007.09.012","volume":"110","author":"S De Raedt","year":"2008","unstructured":"De Raedt S, Lacor P, Michotte A, Martin JJ. Progressive multifocal leukoencephalopathy as first manifestation of sarcoidosis. Clin Neurol Neurosurg. 2008;110:186\u20139. https:\/\/doi.org\/10.1016\/j.clineuro.2007.09.012.","journal-title":"Clin Neurol Neurosurg"},{"key":"1973_CR9","doi-asserted-by":"publisher","first-page":"258","DOI":"10.1159\/000333780","volume":"3","author":"JH Park","year":"2011","unstructured":"Park JH, Ryoo S, Noh HJ, Jeon B. Dual therapy with cidofovir and mirtazapine for progressive multifocal leukoencephalopathy in a sarcoidosis patient. Case Rep Neurol. 2011;3:258\u201362. . https:\/\/doi.org\/10.1159\/000333780","journal-title":"Case Rep Neurol"},{"issue":"5","key":"1973_CR10","doi-asserted-by":"publisher","first-page":"970","DOI":"10.3390\/v14050970","volume":"14","author":"C Pinnetti","year":"2022","unstructured":"Pinnetti C, Cimini E, Vergori A, Mazzotta V, Grassi G, Mondi A, et al. Use of pembrolizumab for treatment of progressive multifocal leukoencephalopathy in people living with HIV. Viruses. 2022;14(5):970. https:\/\/doi.org\/10.3390\/v14050970.","journal-title":"Viruses"}],"container-title":["The Cerebellum"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1007\/s12311-026-01973-9.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/article\/10.1007\/s12311-026-01973-9","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1007\/s12311-026-01973-9.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,16]],"date-time":"2026-06-16T19:03:50Z","timestamp":1781636630000},"score":1,"resource":{"primary":{"URL":"https:\/\/link.springer.com\/10.1007\/s12311-026-01973-9"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,28]]},"references-count":10,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["1973"],"URL":"https:\/\/doi.org\/10.1007\/s12311-026-01973-9","relation":{},"ISSN":["1473-4230"],"issn-type":[{"value":"1473-4230","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,28]]},"assertion":[{"value":"17 November 2025","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"14 February 2026","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"28 February 2026","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"This article reports a single clinical case. According to institutional policy, formal ethics committee approval was not required.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical Approval"}},{"value":"Written informed consent for publication of clinical details and images was obtained from the patient.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Informed Consent"}},{"value":"The authors declare no competing interests.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}},{"value":"Not applicable.","order":5,"name":"Ethics","group":{"name":"EthicsHeading","label":"Clinical Trial Number"}}],"article-number":"26"}}