Introduction: Muscle weakness in thyroid disease is commonly attributed to thyrotoxic myopathy or hypokalemic periodic paralysis. Nevertheless, autoimmune conditions such as idiopathic inflammatory myopathies (IIM) and myasthenia gravis (MG) should be considered, as they may coexist with Graves’ disease. Case: A 54-year-old female with hypertension and Graves’ disease, treated with carbimazole for 2 years, had her therapy discontinued after remission. She was restarted on low-dose carbimazole following symptom recurrence. Three weeks later, she developed progressive proximal weakness, dysphagia, hoarseness, anorexia, and weight loss. On examination, body mass index was 22 kg/m² with mild proptosis, symmetrical proximal weakness (MRC 4/5), and erythematous rashes on thighs and shins. Otorhinolaryngology evaluation confirmed bilateral vocal cord palsy. Investigations revealed markedly elevated creatine kinase (7,950 U/L), aspartate aminotransferase (349 U/L), and alanine aminotransferase (179 U/L), with euthyroid biochemistry (thyroid-stimulating hormone 5.21 mIU/L, free thyroxine 4 16.6 pmol/L). Hypokalemia correction failed to improve symptoms, excluding periodic paralysis. ANA, C3, and C4 were normal. Myositis panel showed strong anti-Cytosolic 5’-nucleotidase 1A positivity with borderline anti-Ro-52. A diagnosis of IIM with bulbar involvement was made. She was treated with intravenous methylprednisolone and intravenous immunoglobulin, with clinical improvement. Conclusion This case highlights the diagnostic challenge of muscle weakness in thyroid disease. While thyrotoxic myopathy is often presumed, markedly elevated creatinine kinase, rash, and bulbar involvement should prompt suspicion of IIM. Early immunosuppressive therapy is essential to achieve favorable outcomes.
Muscle Weakness ; Thyroid Diseases ; Muscular Diseases