A 34-year-old woman comes to the office due to fatigue for the last several months. She becomes tired easily after walking short distances. She also has difficulty combing her hair due to problems holding her hands over her head for long periods. The patient reports anxiety, irritability, and an unintentional weight loss of 3.6 kg (8 lb) over the last 2 months. She has no fever or loss of appetite. The patient does not use tobacco or alcohol. Her father died of a stroke at age 54 and her mother has diabetes mellitus. On examination, the patient is afebrile with a pulse of 115/min. Cardiac examination reveals regular tachycardia with no murmur. The lungs are clear to auscultation. The patient's gait is normal, but she awkwardly drops into the chair when asked to slowly sit. The patient appears to have decreased muscle mass in her shoulders, but her muscles are nontender. Deep tendon reflexes are normal. Which of the following is the most likely cause of this patient's symptoms?

Question

A 34-year-old woman comes to the office due to fatigue for the last several months.  She becomes tired easily after walking short distances.  She also has difficulty combing her hair due to problems holding her hands over her head for long periods.  The patient reports anxiety, irritability, and an unintentional weight loss of 3.6 kg (8 lb) over the last 2 months.  She has no fever or loss of appetite.  The patient does not use tobacco or alcohol.  Her father died of a stroke at age 54 and her mother has diabetes mellitus.  On examination, the patient is afebrile with a pulse of 115/min.  Cardiac examination reveals regular tachycardia with no murmur.  The lungs are clear to auscultation.  The patient's gait is normal, but she awkwardly drops into the chair when asked to slowly sit.  The patient appears to have decreased muscle mass in her shoulders, but her muscles are nontender.  Deep tendon reflexes are normal.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d3bc_6a0e_bc81_3fd124f4bdbb_MD0003_00 This patient has proximal muscle weakness (eg, difficulty combing hair, weakness getting into or out of a chair) consistent with myopathy. This type of myopathy can be due to drugs (eg, glucocorticoids) or to connective tissue (eg, polymyositis/dermatomyositis), endocrine (eg, hypothyroidism or hyperthyroidism, Cushing disease), and neuromuscular (eg, Lambert-Eaton syndrome, myasthenia gravis) diseases. This patient has multiple features suggesting hyperthyroidism as the cause of her myopathy, including anxiety, tachycardia, and weight loss. Fatigue is common in hyperthyroidism due to chronic sympathetic hyperstimulation. Although hyperthyroidism is classically associated with hyper-reflexia, reflexes are frequently normal. Acute thyrotoxic myopathy can present with severe distal or proximal muscle weakness, usually without bulbar or respiratory muscle involvement. Chronic hyperthyroid myopathy presents with proximal muscle weakness weeks to months after the onset of hyperthyroidism. Objective findings may include muscle atrophy. Treatment of hyperthyroidism usually improves the myopathy. (Choice A) Parkinson disease involves primarily the basal ganglia. However, it is uncommon in individuals age <40, and this patient also has no other characteristic findings (eg, resting tremor, rigidity, postural instability). (Choice B) Cerebellar disorders typically present with gait and balance problems due to unsteadiness or incoordination in the legs. Proximal muscle weakness and/or atrophy are unusual. (Choice C) Polymyositis, an inflammatory myopathy most common in middle-age women, presents with symmetric proximal muscle weakness and tenderness. However, muscle atrophy is a late finding, and this patient has other features (eg, tachycardia, weight loss) that make thyroid disease more likely. (Choice D) Myasthenia gravis is due to autoantibodies against the postsynaptic membrane of the neuromuscular junction. Features include ocular (ptosis, diplopia) and facial weakness as well as bulbar muscle weakness that is worse on repetitive tasks. Isolated proximal muscle weakness is atypical. (Choice E) Peripheral motor neuropathies typically present with distal muscle weakness and decreased deep tendon reflexes and frequently have associated sensory symptoms. (Choice G) Upper motor neuron disease (eg, primary lateral sclerosis) causes slowness, stiffness, and clumsiness of movement rather than proximal muscle weakness and atrophy. Examination typically shows long tract signs (eg, hyper-reflexia, spasticity). Educational objective: Chronic hyperthyroid myopathy is characterized by proximal muscle weakness in the setting of clinical features of hyperthyroidism. Objective findings may include muscle atrophy. Treatment of hyperthyroidism usually improves the myopathy.

A 34-Year-Old Woman Comes to the Office Due to Fatigue