A 48-year-old man comes to the office due to progressive weakness for the past 2 months. The patient has experienced difficulty climbing stairs, especially when carrying heavy items such as groceries, and his symptoms have become progressively worse. He also reports occasional fevers, but no significant pain in the muscles or joints. The patient has had no diplopia, dyspnea, dysphagia, abdominal pain, or heat or cold intolerance. He has a history of hypertension and hyperlipidemia, for which he has taken losartan and atorvastatin, respectively, for the last 4 years. The patient does not use tobacco, alcohol, or illicit drugs. Temperature is 37.1 C (98.8 F), blood pressure is 132/84 mm Hg, pulse is 72/min, and respirations are 14/min. He has no scleral icterus. Cardiopulmonary examination is normal. The abdomen is soft and nontender with no hepatosplenomegaly. Muscle strength is 3/5 in the deltoids and hip flexors but is otherwise normal. Deep tendon reflexes are normal and symmetric, and sensations to pain and light touch are intact. There is mild muscle tenderness and some of the small joints of both hands are tender to palpation without any swelling or erythema. He has no skin rash. Laboratory results are as follows:

Which of the following is the most likely cause of this patient's current symptoms?

Question

A 48-year-old man comes to the office due to progressive weakness for the past 2 months.  The patient has experienced difficulty climbing stairs, especially when carrying heavy items such as groceries, and his symptoms have become progressively worse.  He also reports occasional fevers, but no significant pain in the muscles or joints.  The patient has had no diplopia, dyspnea, dysphagia, abdominal pain, or heat or cold intolerance.  He has a history of hypertension and hyperlipidemia, for which he has taken losartan and atorvastatin, respectively, for the last 4 years.  The patient does not use tobacco, alcohol, or illicit drugs.  Temperature is 37.1 C (98.8 F), blood pressure is 132/84 mm Hg, pulse is 72/min, and respirations are 14/min.  He has no scleral icterus.  Cardiopulmonary examination is normal.  The abdomen is soft and nontender with no hepatosplenomegaly.  Muscle strength is 3/5 in the deltoids and hip flexors but is otherwise normal.  Deep tendon reflexes are normal and symmetric, and sensations to pain and light touch are intact.  There is mild muscle tenderness and some of the small joints of both hands are tender to palpation without any swelling or erythema.  He has no skin rash.  Laboratory results are as follows:
 
Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

Explanation: This patient has typical features of polymyositis, including progressive, painless proximal muscle weakness with elevated muscle enzymes (eg, creatine kinase, transaminases) and inflammatory markers (eg, C-reactive protein). Polymyositis is an inflammatory myopathy triggered by unknown, possibly viral, antigens. Peak incidence occurs at age 40-50. Proximal muscle weakness typically manifests as difficulty climbing stairs, getting into or out of a low chair or car, or working with the arms overhead (eg, combing hair). Joint pain (as in this patient) or swelling may be present. Polymyositis can also involve the upper esophageal musculature, leading to dysphagia with regurgitation and aspiration. Dermatomyositis is a similar disorder, but with characteristic skin manifestations. skin manifestations Most patients have detectable autoantibodies (eg, antinuclear antibody, anti-Jo-1). Definitive diagnosis is established on muscle biopsy. Polymyositis and dermatomyositis may occur as paraneoplastic syndromes, so patients should undergo careful examination and age-appropriate screening tests. (Choice A) Statin myopathy typically presents with mild muscular pain, although patients may occasionally experience severe myopathy with elevated creatine kinase levels. However, statin myopathy is not classically associated with joint pain and usually occurs in the first few months of therapy; it is unlikely in this patient on chronic therapy. (Choice B) Hypothyroid myopathy is a common cause of muscle weakness and can be associated with creatine kinase elevation. However, it is typically also associated with myalgias, delayed reflexes, and other symptoms of hypothyroidism. This patient has an elevated TSH consistent with subclinical hypothyroidism, but his thyroxine level is normal. (Choice D) Myasthenia gravis typically causes fatigability (ie, normal initial muscle strength that fades with repeated use) rather than weakness, although proximal muscle symptoms may resemble polymyositis. However, most patients have facial/oculobulbar symptoms, and muscle enzyme levels are normal. (Choice E) Polymyalgia rheumatica is very rare in younger patients (age <50), and typically causes stiffness and pain rather than painless weakness. Educational objective: Polymyositis is characterized by painless proximal muscle weakness with elevated muscle enzymes and inflammatory markers. Peak incidence occurs at age 40-50. Muscle weakness may manifest as difficulty climbing stairs, getting into or out of a chair or car, or working with the arms overhead. Dermatomyositis is a similar disorder but with characteristic skin manifestations. References: The diagnosis and classification of polymyositis. (http://www.ncbi.nlm.nih.gov/pubmed/24461380)

A 48-Year-Old Man Comes to the Office Due to Progressive