Nolla Solé, Joan MiquelNarváez García, Francisco Javier2025-11-262025-11-262025-11https://hdl.handle.net/2445/224440This document is part of the Clinical Cases for Residents collection, a teaching project aimed at postgraduate training in Rheumatology and also applicable to other medical specialties involved in the management of systemic diseases. Its purpose is to strengthen clinical reasoning skills, syndromic analysis, and the structured development of differential diagnoses in complex clinical scenarios. The case presents the comprehensive evaluation of a 64-year-old man with advanced lung carcinoma receiving immune checkpoint inhibitor therapy, who develops progressive dyspnea, ptosis, diplopia, and symmetrical proximal muscle weakness. A detailed discussion of the differential diagnoses is provided, with particular emphasis on the reasoning that supports immune checkpoint inhibitor–related toxicity with the characteristic triple overlap of myositis, myocarditis, and myasthenia gravis. The document outlines the key elements required for clinical interpretation, the complementary tests needed—including neuromuscular, biochemical, and cardiac evaluation—and the underlying pathophysiological considerations. The case is designed as a teaching tool for medical residents, with activities focused on group discussion, structured diagnostic reasoning, and the integration of clinical, analytical, and imaging findings. It forms part of a collection intended to reinforce advanced competencies in differential diagnosis, integrative clinical analysis, and evidence-based decision-making in real-world clinical practice.4 p.application/pdfengcc by-nc-nd (c) Nolla Solé, Joan Miquel et al., 2025http://creativecommons.org/licenses/by-nc-nd/3.0/es/ReumatologiaMedicina internaOncologiaFormulació clínicaEstudi de casosinfo:eu-repo/semantics/otherinfo:eu-repo/semantics/openAccess