MON-382 - A Case of Mistaken Identity: Myxedema Coma Presenting as Acute Stroke and Cardiac Arrest

Introduction:
Myxedema coma (MC) is a rare, life-threatening manifestation of hypothyroidism that often mimics acute neurologic or cardiovascular emergencies, leading to diagnostic delays and high mortality with delayed treatment. Classic features include altered mental status, hypothermia, and bradycardia. However, symptoms may overlap with stroke, sepsis, or cardiogenic shock. We present a case of MC mimicking acute stroke, complicated by cardiac arrest, demonstrating the critical need for high clinical suspicion and early endocrine-directed therapy.

Case Description:
A 79-year-old woman with known hypothyroidism, coronary artery disease, atrial fibrillation (not on amiodarone), and chronic kidney disease presented to the hospital with hypothermia (34°C), acute dysarthria, and confusion, prompting stroke protocol activation. During imaging, she developed agonal respirations and pulselessness. Cardiopulmonary resuscitation was initiated, achieving return of spontaneous circulation after seven minutes. ECG showed junctional bradycardia (HR 34) and QTc prolongation (610 ms). Labs confirmed severe hypothyroidism: TSH 133 µIU/mL, free T4 0.5 ng/dL. Imaging showed bilateral pleural effusions and excluded acute stroke, pulmonary embolism, and aortic dissection; shifting the diagnostic focus to MC, with her myxedema coma diagnostic score being 80 (>60 is diagnostic). Prompt treatment began with IV levothyroxine 200 mcg and stress-dose hydrocortisone. She required mechanical ventilation and vasopressor support for cardiogenic shock. Mental status and hemodynamics improved with thyroid replacement, and she was extubated on day 3 and transitioned to oral levothyroxine. By discharge (day 16), TSH improved to 15.6 µIU/mL, and free T4 to 1.1 ng/dL. A negative cosyntropin test allowed hydrocortisone taper post-discharge. She was discharged on levothyroxine 150 mcg daily.

Discussion:
Myxedema coma's diverse and often atypical presentation poses significant diagnostic challenges, particularly in elderly patients with multiple comorbidities. This case is particularly instructive due to its striking features: initial acute dysarthria/confusion directly mimicked acute stroke (an uncommon but reported MC manifestation). As seen in our case, profound thyroid hormone deficiency led to severe bradycardia, QTc prolongation, myocardial depression, cardiogenic shock, and cardiac arrest. Given potential delays in laboratory confirmation, empiric thyroid hormone replacement and glucocorticoids may be life-saving. Early endocrine consultation and aggressive supportive care are vital. Our case highlights the importance of maintaining high suspicion for MC in patients with unexplained altered mental status, bradycardia, or neurological/cardiovascular instability, along with other critical differentials.

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