Impending myxedema as a manifestation of subclinical hypothyroidism in a case of systemic lupus erythematosus: A case report.

RATIONALE: Myxedema coma, the most severe form of hypothyroidism, is exceedingly rare in the setting of subclinical hypothyroidism. This case highlights the diagnostic challenge of impending myxedema coma in a patient with sepsis and systemic lupus erythematosus (SLE), despite the absence of overt hypothyroid symptoms or signs.

PATIENT CONCERNS: A 28-year-old female with known SLE presented to the emergency department with a 1-week history of cough, shortness of breath, pleuritic chest pain, and high-grade fever. Physical examination revealed hypotension, fever, hypoxia, pallor, oral lesions, and lung crepitations.

DIAGNOSES: Initial investigations showed leukocytosis, elevated inflammatory markers, and imaging consistent with cryptogenic organizing pneumonia. Thyroid function tests revealed elevated thyroid-stimulating hormone with normal free tetraiodothyronine and free triiodothyronine, indicating subclinical hypothyroidism. After excluding an SLE flare and other causes, impending myxedema coma was diagnosed.

INTERVENTIONS: Initial treatment targeted presumed sepsis and pneumonia. Upon suspicion of impending myxedema coma, oral levothyroxine replacement therapy was initiated.

OUTCOMES: Following levothyroxine administration, the patient's mental status and blood pressure improved significantly. She was discharged after 2 weeks of hospitalization and remained asymptomatic at 4-month follow-up.

LESSONS: This case, one of only 6 reported instances of myxedema coma occurring in subclinical hypothyroidism, underscores that this life-threatening condition can develop even without classic hypothyroid features, particularly amidst significant physiological stressors like sepsis and SLE. A high index of suspicion, prompt diagnosis based on biochemical findings, and immediate initiation of thyroid hormone replacement are critical for successful management.