Bismuth subsalicylate (Pepto-Bismol ® ) and other bismuth-containing compounds have been used for many years to treat gastroenterological complaints. Although safe in the majority of patients, bismuth can cause a well-described toxic state marked by progressive neurological decline. Features of bismuth toxicity include confusion, postural instability, myoclonus, and problems with language [1]. This presentation can masquerade as other causes of progressive neurologic dysfunction including Creutzfeld-Jakob Disease (CJD), Hashimoto's Encephalopathy, and others. In this case study, we present a patient who was using bismuth salicylate in toxic quantities to help control diarrhea. On initial presentation, several diagnoses were entertained before bismuth levels were obtained. This case study highlights the fact that bismuth toxicity, while rare, should be considered in a patient with progressive neurological decline. Also, we hope this case reminds physicians of a severe consequence of a common, readily available medication.Keywords: Bismuth Toxicity; Creutzfeld-Jakob Case ReportA 56 year old woman who had recently begun treatment for collagenous colitis presented to her local hospital with several days of psychomotor retardation, decreased concentration, tremor of her hands, visual hallucinations, and postural instability preventing her from standing on her own. The patient was concurrently being treated on stable doses of medications for irritable bowel syndrome, hypertension, hypothyroidism, and depression.Her husband stated that her concentration had been gradually decreasing for the previous two weeks but had profoundly worsened in the last couple days. There is no record that the patient saw a clinician for mental status deterioration prior to her hospital presentation. During her stay at the hospital, the patient became more delirious and somnolent and began to experience myoclonic jerks and hyperreflexia. Serotonin syndrome was considered, and the patient's serotonergic medications (escitalopram, duloxetine) were held. The patient's lack of improvement over the next three days resulted in transfer to a teaching hospital, where she was admitted to the Neurology Service.Initial physical exam showed temperature 37.0 degrees Celsius, blood pressure 165/94 mm Hg, pulse 117, respirations 16, oxygen saturations 98% on room air. The patient provided one word answers to questions, was lethargic with impaired attention, and could express orientation correctly only to person. Cranial nerves II-XI were intact, but patient could not protrude tongue. Muscle bulk and strength were normal, but tone was markedly rigid throughout. She demonstrated frequent myoclonic jerks and occasionally exhibited intention tremor. Reflex examination demonstrated hyperactive spreading reflexes at all stations with upgoing toes bilaterally. All other aspects of the physical exam were unremarkable. Laboratory tests, including thyroid function tests, B12 levels, RPR, and various microbiological assays were within normal limits. A noncon...