Severe Hyponatremic Encephalopathy Induced by Unsupervised "Therapeutic" 3,4-Methylenedioxymethamphetamine Use in a 55-Year-Old Woman: A Diagnostic Pitfall.

While the clinical archetype of 3,4-methylenedioxymethamphetamine (MDMA) toxicity is traditionally associated with young individuals in nightlife environments, particularly in nightclubs and rave settings, its emerging role in therapeutic research may contribute to increasing unsupervised use. As MDMA gains mainstream attention for its potential mental health benefits, particularly for posttraumatic stress disorder, its use may involve a broader demographic, including older individuals in non-recreational contexts. This transition may create a diagnostic pitfall for emergency physicians, particularly through representativeness bias - the tendency to judge a clinical situation based on similarity to a stereotypical category without regard to underlying base rates. When severe hyponatremia occurs in an older patient during a mundane social setting, toxic etiologies may be overlooked, as the presentation does not match the expected profile of MDMA toxicity typically seen in younger individuals. We report a life-threatening case of MDMA-induced hyponatremic encephalopathy in a 55-year-old woman, occurring in a private domestic setting. The patient developed severe hyponatremia with neurological deterioration following self-directed "therapeutic" MDMA use. This case highlights the need to reconsider the demographic and contextual profile of synthetic drug toxicity in the era of emerging psychedelic-assisted therapy research and underscores the importance of maintaining a broad differential diagnosis for unexplained hyponatremia with altered mental status, regardless of patient age or social context.