Background: Thyroid storm is a life-threatening health condition associated with hyperthyroidism. Apathetic hyperthyroidism is an atypical presentation of the thyrotoxicosis spectrum; this atypical presentation of apathetic thyroid storm makes the diagnosis of thyroid storm more challenging. Case Presentation: A previously healthy 23-year-old female presented to the emergency department with a 3-hour history of inability to talk or move limbs. Initial clinical examination showed that patient was conscious, alert, and febrile, with no external rashes or neck stiffness but was unable to move all limbs. Increased reflexes in all four limbs with no clonus and no rigidity was found. There was no sign of stroke in computed tomography scan, and other neurological assessments were normal. Cardiac examination showed persistent sinus tachycardia reaching 160 heartbeats per minute, despite antipyretic and fluid treatment. This finding raised the suspicion of hyperthyroidism and thyrotoxicosis. Thyroid function test revealed thyroid stimulating hormone level of 0.005 μlU/ml, free thyroxine >100, and free triiodothyronine of 41. Patient was admitted and treatment of anti-thyroid medication, steroid, and beta-blocker was initiated. The condition improved and patient was discharged home. Conclusion: The diagnosis of apathetic hyperthyroidism is difficult and sometimes delayed owing to its atypical presentation. The patient could potentially quietly sink into coma, if high index of suspicion is not maintained.

Keywords: thyroid storm, conversion disorder, endocrine emergency, hyperthyroidism, apathetic hyperthyroidism