(255) A Critical Case of Clinical Myxedema Coma With Atypical Thyroid Function Tests

Introduction: Myxedema coma (MC) is a life-threatening condition that typically presents in patients with chronically uncontrolled hypothyroidism. It is primarily due to a lack of compensatory thyroid hormone stimuli in response to physiological stressors. Key features are altered mental status (AMS) and defective thermoregulation with gradual progression to potential coma; other features include bradycardia and swelling of the face and oral mucosa. Thyroid function testing (TFT) typically shows elevated thyroid stimulating hormone (TSH) and low-to-undetectable levels of free T4. Rarely, patients may present with all the clinical signs of MC, however with atypical TFT values.

Description: A 93 year-old woman presents with AMS, weakness, and fatigue. She had recently been treated for a urinary tract infection and subsequently developed infectious colitis. She was hypothermic, bradycardic, and hypotensive, and had significantly edematous oral mucosa with copious salivary secretions. She was admitted to the Intensive Care Unit due to high concern for airway compromise. Antibiotics were initiated for suspected sepsis. Initial laboratory and imaging studies were unremarkable. Hydrocortisone and levothyroxine were initiated due to a strong clinical suspicion for MC. Testing later revealed elevated TSH, undetectably low T3, and normal free T4 levels. Upon further investigation, TSH levels on prior hospitalizations were found to be elevated, however she was never started on therapy. She clinically improved on treatment.

Discussion: This patient presented with classic clinical features of MC, however laboratory studies interestingly showed a normal free T4 value. Currently, there is no clear diagnostic criteria for MC, however a proposed Myxedema Coma Score has been developed with a score of > 60 being highly suggestive/diagnostic for MC; this patient had a score of 95, making MC the most likely diagnosis despite atypical TFT. This case illustrates why the diagnosis and subsequent management of MC should not be solely based on TFT as it can be widely variable and affected by comorbid conditions and physiological factors. Instead, clinicians should use suspicious clinical features to guide diagnosis and management, especially in Critical Care Medicine where these critical cases are most commonly encountered.