Hypomagnesemia: An Overlooked Cause of Delirium and Cardiac Complications in an Elderly Patient.

Delirium is a frequent complication in elderly patients and is often multifactorial, with electrolyte imbalances representing a major contributor. While sodium, potassium, and calcium disorders are commonly evaluated, hypomagnesemia is an overlooked but clinically significant cause of both neurological and cardiac manifestations. Magnesium is essential for neuronal stability, neurotransmitter regulation, and calcium channel modulation. Its deficiency can lead to neuropsychiatric symptoms, arrhythmias, and myocardial injury. We report the case of an 81-year-old woman who presented with acute confusion following several days of diarrhea. Investigations revealed severe hypomagnesemia (serum magnesium: 0.3 mmol/L), ST-segment depression, prolonged QT interval, and elevated troponin levels. She was managed as a type 2 myocardial infarction in the context of sepsis and electrolyte imbalance. Prompt intravenous magnesium replacement resulted in rapid resolution of delirium and cognitive improvement. This case underscores the importance of routine assessment of magnesium levels in elderly patients presenting with delirium, especially in the presence of gastrointestinal losses or cardiovascular comorbidities, and highlights the reversibility of neurological and cardiac complications when deficiency is corrected.