Answer
D: Thyroid storm
Educational Objective
Diagnose thyroid storm.
Critique
The most likely diagnosis is thyroid storm. Thyroid storm is characterized by severe thyrotoxicosis associated with systemic decompensation. Presentation often follows a precipitating event, such as non-thyroid surgery as in this patient's case. Clinical manifestations include high fever, altered mental status and seizures, tachycardia, atrial fibrillation and heart failure, and hepatic dysfunction. A diagnostic system, such as the Burch and Wartofsky Point Scale, can support the diagnosis with scores greater than or equal to 45 being highly suggestive. The patient's thyroid function tests should be assessed to confirm recurrent hyperthyroidism and aggressive treatment should be initiated in the ICU. Management includes treatment of any precipitant illness, supportive care, and thyrotoxicosis-directed therapy including 尾-adrenergic blockers (esmolol infusion), antithyroid drug therapy, intravenous glucocorticoids, and potassium iodide. Plasmapheresis and emergent thyroidectomy are utilized in patients who cannot be sufficiently managed with medical therapy alone.
Adrenal crisis is not the most likely diagnosis. Although autoimmune primary adrenal failure occurs more commonly in patients with other autoimmune disorders, patients with adrenal crisis usually present with hypotension, hyponatremia, and hyperkalemia, in addition to gastrointestinal manifestations. This diagnosis cannot explain the patient's hyperthermia, lid lag, thyromegaly, brisk reflexes, or tremor.
Malignant hyperthermia is an uncommon cause of severe hyperthermia that occurs in genetically susceptible individuals upon exposure to a volatile anesthetic such as halothane or isoflurane. Symptoms begin intraoperatively or in postoperative recovery, not 3 days following surgery. Features include mixed respiratory and metabolic acidosis, muscle rigidity, hyperkalemia, and rhabdomyolysis. This diagnosis does not explain the patient's thyrotoxicosis-related findings. Finally, the patient lacks muscle rigidity, a pathognomonic finding in malignant hyperthermia.
Myxedema coma is also unlikely. Although patients with myxedema coma may experience cardiac dysfunction and mental status changes, this patient is presenting with signs and symptoms of thyroid hormone excess, not deficiency. She has a history of Graves disease in remission after treatment with antithyroid drug therapy. She has not received radioactive iodine or thyroidectomy and thus the development of hypothyroidism at this point would be unusual.
Key Point
Thyroid storm is a severe manifestation of thyrotoxicosis with life-threatening secondary systemic decompensation; it occurs most commonly with underlying Graves disease coupled with a precipitating factor such as surgery.
Bibliogrpahy
De Leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet. 2016;388:906-18. [PMID: 27038492] doi:10.1016/S0140-6736(16)00278-6