A Case Report on Bismuth-Induced Encephalopathy Secondary to Pepto-Bismol.

Bismuth subsalicylate is a widely available over-the-counter medication commonly used for gastrointestinal symptoms. Although generally considered safe, prolonged use can result in systemic toxicity, including severe neurological manifestations that are often underrecognized. We report the case of a 77-year-old man with microscopic colitis, lymphocytic subtype, who developed progressive encephalopathy, proximal muscle weakness, tremor, and gait instability after more than two years of daily bismuth subsalicylate use. His clinical course was marked by fluctuating neurological symptoms, multiple hospitalizations, extensive negative diagnostic evaluations, and an initial misdiagnosis of a Parkinsonian disorder. Serum testing ultimately revealed markedly elevated bismuth levels. Discontinuation of bismuth subsalicylate and supportive care resulted in gradual clinical improvement, with normalization of serum bismuth levels and gradual neurological recovery over several months. This case highlights the diagnostic challenges associated with bismuth-induced neurotoxicity and underscores the importance of thorough medication reconciliation, including over-the-counter agents. Increased clinician awareness is critical, as prompt recognition and discontinuation of bismuth-containing products can lead to substantial neurological recovery and prevent unnecessary diagnostic interventions.