Clinical Reasoning: A 73-Year-Old Man With Progressive Proximal Muscle Weakness and Binocular Diplopia

Progressive weakness and diplopia have a wide differential diagnosis, which can be narrowed by obtaining a detailed history and performing a careful physical examination. It is essential to determine whether these 2 symptoms are due to a single, unifying process or separate processes. We review the case of a 73-year-old man with progressive proximal lower than upper extremity weakness, followed by binocular horizontal diplopia. Clinical history, with attention to rate of progression and associated symptomatology, guided our diagnostic approach and final diagnosis.