A Case of Rhabdomyolysis in a Patient With Hashimoto’s Thyroiditis

Introduction: Hashimoto’s thyroiditis (HT) is an autoimmune disease that presents with musculoskeletal symptoms like proximal muscle weakness, stiffness, pain or cramps in the majority of patients. Rhabdomyolysis which is a breakdown of the skeletal muscles, is a rare but serious manifestation of hypothyroidism and if occurs, it is usually related to trauma, strenuous exercise or use of statins. We report a patient with unrecognized Hashimoto’s thyroiditis who presented with severe rhabdomyolysis without reported history of strenuous exercise, seizures or statin use and surprisingly, He did not have any complications from rhabdomyolysis like electrolytes abnormalities or acute kidney injury. Case Report: A 56-year-old man with no reported past medical history who presented with severe generalized weakness, bilateral leg pain, and recurrent falls for three months. He also reported constipation, fatigue and dry skin. Denied any prior personal or family history of thyroid disease, seizure disorder, statin use, trauma or tick bite. He was afebrile with a heart rate of 80 beats/minute, a blood pressure of 126/71mmHg. Initial laboratory testing showed normal metabolic panel, elevated thyroid stimulating hormone 30.6 uIU/mL (Range 0.27-4.2 uIU/mL), FT4 0.1 ng/dL (Range 0.93-1.7ng/dL), TPO Ab 300IU/mL (N<43IU/mL), Creatine Kinase (CK) level 10,000U/L (N<200U/L), ESR 27 mm/Hr (N<20mm/Hr) and Lactate Dehydrogenase 621U/L (N <225U/L). A muscle biopsy was done to rule out polymyositis as a cause of his severe muscle pain, weakness and tenderness and it was negative. Patient was diagnosed with HT with associated rhabdomyolysis after excluding other causes of rhabdomyolysis. Supportive treatment with intravenous fluids and Levothyroxine were initiated and resulted in dramatic clinical improvement. Conclusion: Rhabdomyolysis is a rare but potentially a serious complication of hypothyroidism. Screening for hypothyroidism in patients with elevated muscle enzymes should be considered, as early diagnosis and prompt treatment of hypothyroidism is essential to prevent rhabdomyolysis and its consequences like acute kidney disease and electrolytes abnormalities. Appropriate fluid resuscitation is the mainstay therapy for AKI prevention and should be initiated in a timely manner. Key Words: HT: Hashimoto’s Thyroiditis, ESR: Erythrocyte Sedimentation Rate, TPO Ab: Thyroid Peroxidase Antibody, TSH: Thyroid Stimulating Hormone, FT4: Free Thyroxine level, AKI: Acute Kidney Injury.