Mistaken Muscles: Myxedema Coma Misdiagnosed as Polymyositis Leading to Delayed Treatment

Case Diagnosis: An 83-year-old male with chronic sinusitis, presumed polymyositis on long-term prednisone therapy, and prior FESS (functional endoscopic sinus surgery) presented with lethargy, cough, sore throat, and sinus congestion, later diagnosed with profound central hypothyroidism and myxedema coma.

Case Description or Program Description: Post-FESS, the patient performed sinus rinses twice daily for ten years. This episode was initially considered an acute flare of chronic sinusitis. Over two years, he reported increased lethargy, darkening and fragile skin, thinning hair, morning fatigue, hoarseness, edematous legs despite Lasix, cold intolerance, and muscle weakness. Outpatient doctors diagnosed polymyositis, prescribing 10mg prednisone BID.

Setting: Community Hospital

Assessment/Results: At the hospital, he was difficult to arouse, with hoarse voice, brittle nails and skin, and brawny edema. Low TSH and T4 prompted an MRI, revealing postsurgical changes from FESS and minimal pituitary tissue, suggesting hypopituitarism. He received IV levothyronine, levothyroxine, and hydrocortisone, improving dramatically and enabling therapy participation. Prolonged symptoms led to a maladaptive swallowing mechanism, requiring aggressive speech therapy to prevent aspiration.

Discussion (relevance): Polymyositis typically shows symmetric proximal weakness, elevated CK, abnormal EMG, and inflammation on biopsy. This patient’s additional symptoms—skin changes, hair thinning, hoarseness, and cold intolerance—were atypical. Normal CK and EMG findings should have prompted consideration of alternative diagnoses, particularly endocrine myopathy, which can mimic inflammatory myopathies but lacks the aforementioned hallmark findings. Worsening symptoms despite two years of prednisone, which usually improves polymyositis, further indicated a misdiagnosis.

Conclusions: This delay might have been avoided with greater inquiry into the initial low TSH, rather than attributing it to steroid-induced suppression. Early recognition could have prevented myxedema coma, swallowing dysfunction, and steroid side effects like hyperglycemia and immunosuppression. This case highlights the need for thorough endocrine evaluation in atypical myopathic presentations, emphasizing the risks of premature diagnostic closure and the benefits of interdisciplinary care for optimal outcomes.