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Pembrolizumab therapy was initiated, which led to acute renal failure after the first infusion. The case highlights the high pathogenicity of MCC and the risk of renal complication associated with pembrolizumab, underscoring the need for vigilance in anticipating and preventing such adverse effects. The discussion examines recent recommendations on the best treatment options for metastatic MCC, which currently includes immunotherapy.<\/jats:p>","DOI":"10.1136\/bcr-2025-266245","type":"journal-article","created":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T14:05:27Z","timestamp":1771941927000},"page":"e266245","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Fatal outcome after immunotherapy in metastatic Merkel cell carcinoma of unknown primary cause"],"prefix":"10.1136","volume":"19","author":[{"given":"Yohan","family":"Depierre","sequence":"first","affiliation":[{"name":"Service of Internal Medicine, Department of Medicine, Network Hospital Neuch\u00e2tel, La Chaux-de-Fonds, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amina Faiza","family":"Chouiter-Djebaili","sequence":"additional","affiliation":[{"name":"Service of Oncology, Department of Oncology, Network Hospital Neuch\u00e2tel, La Chaux-de-Fonds, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Herv\u00e9","family":"Zender","sequence":"additional","affiliation":[{"name":"Service of Internal Medicine, Department of Medicine, Network Hospital Neuch\u00e2tel, La Chaux-de-Fonds, Switzerland"},{"name":"Service of Intensive Care, Department of Acute Medicine, Geneva University Hospitals, Geneva, GE, Switzerland"},{"name":"Faculty of medicine, University of Geneva, Michel Servet 1, 1211 Geneva 4, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chiheb","family":"Said","sequence":"additional","affiliation":[{"name":"Service of Internal Medicine, Department of Medicine, Network Hospital Neuch\u00e2tel, La Chaux-de-Fonds, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,2,24]]},"reference":[{"key":"2026022406050961000_19.2.e266245.1","doi-asserted-by":"crossref","first-page":"2596","DOI":"10.1016\/j.jid.2021.04.007","article-title":"International Increases in Merkel Cell Carcinoma Incidence Rates between 1997 and 2016","volume":"141","author":"Olsen","year":"2021","journal-title":"J Invest Dermatol"},{"key":"2026022406050961000_19.2.e266245.2","doi-asserted-by":"crossref","first-page":"382","DOI":"10.1001\/jamadermatol.2021.6096","article-title":"Recurrence and Mortality Risk of Merkel Cell Carcinoma by Cancer Stage and Time From Diagnosis","volume":"158","author":"McEvoy","year":"2022","journal-title":"JAMA Dermatol"},{"key":"2026022406050961000_19.2.e266245.3","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1111\/bjd.13870","article-title":"Merkel cell carcinoma and Merkel cell polyomavirus: a systematic review and meta-analysis","volume":"173","author":"Santos-Juanes","year":"2015","journal-title":"Br J Dermatol"},{"key":"2026022406050961000_19.2.e266245.4","doi-asserted-by":"publisher","DOI":"10.1016\/j.jaad.2017.10.028"},{"key":"2026022406050961000_19.2.e266245.5","doi-asserted-by":"crossref","unstructured":"Mohsen ST , Price EL , Chan A , et al . 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