A 44-year-old man comes to the physician because of muscle cramps and stiffness involving his legs over the last two weeks. He also describes fatigue and needs to rest after walking several blocks. His other medical problems include type 2 diabetes mellitus, hyperlipidemia, and migraine headaches. His medications include metformin, low-dose aspirin, glyburide, and simvastatin. He was recently started on daily verapamil for migraine prevention. He has a strong family history of diabetes and coronary artery disease.
His blood pressure is 123/70 mm Hg and his pulse is 70/min. His BMI is 31 kg/m². There is no muscle tenderness on physical examination. Muscle strength is 5/5 bilaterally and deep tendon reflexes are 2+ and symmetrical bilaterally.
Laboratory results are as follows:

Which of the following is the most appropriate next step in managing this patient?

Question

A 44-year-old man comes to the physician because of muscle cramps and stiffness involving his legs over the last two weeks. He also describes fatigue and needs to rest after walking several blocks. His other medical problems include type 2 diabetes mellitus, hyperlipidemia, and migraine headaches. His medications include metformin, low-dose aspirin, glyburide, and simvastatin. He was recently started on daily verapamil for migraine prevention. He has a strong family history of diabetes and coronary artery disease.
His blood pressure is 123/70 mm Hg and his pulse is 70/min. His BMI is 31 kg/m². There is no muscle tenderness on physical examination. Muscle strength is 5/5 bilaterally and deep tendon reflexes are 2+ and symmetrical bilaterally.
Laboratory results are as follows:

Which of the following is the most appropriate next step in managing this patient?

Quizplus · Accepted Answer

11ec193a_973d_57f9_853d_63f3a9285185_MD0002_00 This patient's presentation is concerning for statin myopathy, likely due to a drug-drug interaction between verapamil and simvastatin. However, statins can also unmask underlying metabolic muscle disorders (as shown in the above table) and mimic statin myopathy. Patients should have a thorough history and physical examination to look for clues suggesting underlying disorders. All patients should undergo testing for vitamin D levels, thyroid function, and serum CK level. Further testing is dictated by clinical and laboratory findings. (Choice A) Antinuclear antibodies and ESR can evaluate for connective tissue disease (e.g., SLE, polymyalgia rheumatica), but this patient's lack of systemic symptoms (i.e., fever, rash, arthralgias) makes this less likely. (Choice B) Electromyography and nerve conduction studies can diagnose peripheral neuropathy or inflammatory myopathy. However, this patient's normal neurological examination and CK level makes these disorders unlikely. (Choice C) Serum lactate and carnitine levels can diagnose metabolic myopathies (e.g., carnitine palmitoyltransferase II deficiency, McArdle disease). These patients usually present with chronic exercise-induced episodes of muscle weakness, which is not present in this patient. Metformin-induced lactic acidosis is unlikely with normal serum creatinine. (Choice D) A morning serum cortisol level can evaluate for Addison's disease. However, this patient's stable blood pressure and short duration of symptoms makes this less likely. Educational objective: Statin therapy can sometimes worsen an underlying metabolic muscle disorder that mimics statin myopathy. Patients with suspected statin myopathy should first be tested for serum CK, vitamin D, and thyroid function studies. Further testing is guided by clinical and laboratory findings. __________ References: Statin-associated myopathy. (http://www.ncbi.nlm.nih.gov/pubmed/12672737) Asymptomatic hypothyroidism and statin-induced myopathy. (http://www.ncbi.nlm.nih.gov/pubmed/17872677)

A 44-Year-Old Man Comes to the Physician Because of Muscle