Discussion
Our patient had Basedow’s disease and presented with the rare chief complaint of myalgia. Musculoskeletal symptoms and signs are common in patients with thyroid dysfunction, as the skeletal muscle is a major target of thyroid hormones. 4 Although hypothyroidism is a thyroid function abnormality associated with myalgia, hyperthyroidism is mainly associated with myopathy, such as muscle weakness and wasting. Symptoms of myopathy primarily involve the proximal muscles and rarely the pectoralis major muscle.5 Hyperthyroid myopathy usually resolves after recovery from hyperthyroidism. In the present case, the findings were atypical because there was no muscle weakness, no muscular symptoms, and myalgia was not localised to the muscles. Since myalgia in cases such as the presented one is rare, careful consideration of the complications of concomitant disease is needed, followed by a detailed medical interview, review of the system, and systemic physical examination.
In recent years, cases of myalgia and elevated creatine kinase levels during the treatment of hyperthyroidism have been presented, and the side effects of anti-thyroid drugs and relative hypothyroidism have been proposed as explanations for these muscle symptoms. 5However, the presented case is not consistent with relative hypothyroidism because myalgia was present before treatment. Because T4 abnormalities cause abnormal glycogen degradation, abnormal mitochondrial oxidative metabolism, and abnormal triglyceride turnover, which impair muscle function,6 it is usually seen in hypothyroidism, but may be affected in hyperthyroidism as well. Muscle symptoms caused by Basedow’s disease require attention as they could be complications of other autoimmune diseases. Basedow’s disease is rarely associated with other autoimmune diseases, especially polymyositis and myasthenia gravis. 7, 8 Further, the absence of other features of muscle fatigue and myasthenia gravis in the present case ruled out other autoimmune diseases. Similarly, periodic limb paralysis is a rare and life-threatening complication of Basedow’s disease.9 It is characterised by recurrent episodes of transient, flaccid muscle paralysis and affects the proximal muscles more severely than distal muscles. The clinical course of the presented case and normal serum potassium levels were inconsistent with periodic quadriplegia. Furthermore, vitamin D deficiency can be an aetiological factor for non-specific musculoskeletal pain. 10However, this possibility was ruled out because there was no evidence of vitamin D deficiency in the present case. As in previous reports,11 the improvement in myalgia as well as the simultaneous recovery of hyperthyroidism strongly suggests that hyperthyroidism was the cause of the myalgia. To the best of our knowledge, this is a very rare symptom of Basedow’s disease and has only been reported in two previous cases. 9
In conclusion, we report on a patient with Basedow’s disease who presented with the chief complaint of myalgia, which is a rare symptom. In patients with Basedow’s disease who complain of muscular symptoms, it is important to consider the disease mechanism as well as the presence of other concomitant diseases; thyrotoxicosis could be a differential diagnosis in such patients who present with myalgia.
Informed consent: We obtained informed consent from the patient for publication of this case report.
Data accessibility: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Acknowledgments: None. This study did not receive any funding.
Funding: None. This study did not receive any funding.
An ethics statement: We have obtained informed consent from the patient for publication of this case report.
Conflict of Interest : None. We had no Conflict of Interest.