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http://www.medicine-on-line.com Malaise, weakness, and muscle pain: 1/3 Case 084: Malaise, weakness, and muscle pain Author: Thomas YK Chan MD, PhD, FRCP Affiliation: The Chinese University of Hong Kong A 68-year-old woman presented to the Clinic with a 2-month history of malaise, lower limb weakness, and muscle pain, especially after exercise. She also had aches in and around the finger joints. Otherwise she did not smoke nor consume alcoholic beverages and was on aspirin 80 mg daily and metoprolol 50 mg twice daily for angina pectoris. On examination, her blood pressure was 112/76 mmHg; pulse rate was regular at 50 beats/minute; and respiratory rate was 20/min. She was alert and orientated. Proximal muscle weakness was more marked in the lower limbs (grade 4/5) than in upper limbs (5-/5). Tendon reflexes were normal. There was no joint swelling or tenderness. Results of laboratory investigation showed: Blood counts Reference range Hb 10.6 11.5 – 14.3 g/dL MCV 96 81.0 – 91.0 fL WBC 5.6 4.0 – 10.8 109/L Platelet 256 140 – 380 109/L Na 138 134 – 145 mmol/L K 3.6 3.5 – 5.1 mmol/L Urea 4.5 3.4 – 8.9 mmol/L Creatinine 72 44 – 80 µmol/L ALT 68 < 58 IU/L Total bilirubin 15 < 15 µmol/L Plasma http://www.medicine-on-line.com Malaise, weakness, and muscle pain: 2/3 ECG showed sinus bradycardia (52 beats/min) with mild ST segment depression in leads I, aVL and V1 – V4. Question 1 What is the most likely diagnosis in this patient? (a) Hypothyroidism (b) Polymyositis (c) Primary hypoadrenalism (d) Myasthenia gravis (e) Diabetic neuropathy Question 2 Which 2 of the following diagnostic tests should be ordered? (a) Electromyography (b) Thyroid stimulating hormone (c) Fasting blood sugar (d) Creatine kinase (e) Short ACTH stimulation test Go to end of article for correct answers. General comments 1 In this elderly woman with myopathy, malaise, bradycardia and anemia, hypothyroidism should be suspected and was confirmed by a plasma sTSH of 62.3 mIU/L (Reference range: 0.49 – 4.67). Myopathic features in hypothyroidism commonly involve weakness (usually proximal), myalgias, and cramps. Plasma creatine kinase levels are elevated in most patients with hypothyroidism to a modest extent (often less than 1,000 IU/L) and many of whom do not have clinical myopathy. Our patient’s plasma creatine kinase was 1,137 IU/L (Reference range: 32 – 180). Creatine kinase elevation can be explained on the basis of myofiber degeneration. http://www.medicine-on-line.com Malaise, weakness, and muscle pain: 3/3 General comments 2 The red cell production is affected by various hormones, including thyroxine, glucocorticoids, and testosterone. Endocrine failure is generally accompanied by mild to moderate anemia. In hypothyroidism, a second etiology of anemia is related to decreased requirement of oxygen transportation as there is reduction in metabolic rate and oxygen consumption. General comments 3 In patients with angina, thyroxine supplement must be given in a smaller than usual dose (e.g. 25 µg daily). Angina symptoms and ECG should be followed serially and the dose increased at 4 – 6 week intervals until euthyroid if neither symptoms nor ECG worsens. Correct answers Question 1: (a) Hypothyroidism. Question 2: (b) Thyroid stimulating hormone. (d) Creatine kinase. Further readings Garber JR et al. Managing the challenges of hypothyroidism. Journal of Family Practice 2006; 55: S1-8. Scott KR et al. Hypothyroid myopathy with a strikingly elevated serum creatinie kinase level. Muscle & Nerve 2002; 26: 141-4.