Near and Far

A previously healthy 30-year-old woman presented to the emergency department with 2 weeks of weakness.

True muscle weakness must be distinguished from the more common causes of asthenia. Many systemic disorders produce fatigue, with resulting functional limitation that is often interpreted by patients as weakness. Initial history should focus on conditions producing fatigue, such as cardiopulmonary disease, anemia, connective tissue disease, depression or cachexia related to malignancy, infection, or other inflammatory states. Careful questioning may reveal evidence of dyspnea, poor exercise tolerance, or joint pain as an alternative to actual loss of muscle power. If true weakness is still suspected, attention should be focused on the pattern, onset, anatomic site, and progression of weakness. Muscle weakness is often characterized by difficulty with specific tasks, such as climbing stairs, rising from a chair, raising a hand, or using cutlery. The physical examination is critical in determining whether weakness is due to true loss of motor power. The differential diagnosis of weakness is broad and includes neurologic, infectious, endocrine, inflammatory, genetic, metabolic, and drug-induced etiologies.

She initially experienced 3 days of mild cramps and soreness in her thighs. She then developed weakness that began in her thighs and progressed to involve her lower legs and upper and lower arms. She had difficulty combing her hair. She required the use of her arms to get up from a chair. She grasped onto objects to aid in ambulation around the house. In addition, she described 1 year of moderate fatigue but no fever, weight loss, dyspnea, dysphagia, visual changes, paresthesias, bowel or bladder incontinence, back pain, or preceding gastrointestinal or respiratory illness. She had experienced diffuse intermittent hives, most prominent in her chest and upper arms, for the past several weeks.

History certainly supports true weakness but will need to be confirmed on examination. The distribution began as proximal but now appears diffuse. The presence of myalgia and cramping raises the possibility of noninflammatory myopathies, which are usually more insidious in onset. A severe electrolyte disturbance would be possible, based on the diffuse nature of weakness that was preceded by cramping. The distribution of weakness and lack of bowel or bladder incontinence is reassuring and suggests against a spinal cord disorder; however, a high index of suspicion must be maintained for myelopathy because delayed treatment might result in irreversible paralysis.

The patient’s course also includes hives. Common causes of hives include infections and allergic reactions to medications, foods, and insect stings. Urticaria may also result from systemic disorders, such as vasculitis, lupus, lymphoma, mastocytosis, and paraproteinemias, which can be associated with weakness and fatigue. Although severe weakness in combination with hives makes an infectious and allergic reaction less likely, we still seek to ascertain if the evolving chief complaints of weakness and hives are the result of a single unifying and evolving multisystem disorder or are distinct and unrelated processes.

Her past medical history included fibromyalgia, kidney stones, and gastroesophageal reflux disease. One week prior to presentation, she was prescribed prednisone 60 mg daily for the treatment of hives; the dose had been tapered to 40 mg at presentation, with mild improvement of hives. She recently started doxepin for fibromyalgia and insomnia. She lived at home with her husband and 8-year-old child. She worked as a clerk in a pest control office and denied any pesticide exposure. She denied tobacco, alcohol, or illicit drug use. Her family history included systemic lupus erythematosus (SLE) in her mother and maternal aunt.

Glucocorticoids are associated with myopathy; however, the weakness preceded steroid therapy. Thus, unless there was unknown exposure to high-dose steroid medication to treat recurrent episodes of urticaria earlier in her course, glucocorticoid-related myopathy is unlikely. Fibromyalgia might cause the perception of weakness from pain. However, the history of difficulty combing her hair and rising from a chair suggests actual loss of motor power. The side effects of her medications, such as newly started doxepin, must be reviewed. A family history of SLE raises concern for rheumatologic conditions; however, one might expect improvement with steroid therapy.

On physical examination, her temperature was 36.9 °C, blood pressure 126/93 mmHg, pulse 81 beats per minute, respiratory rate 16 breaths per minute, and oxygen saturation 100% on ambient air. Her cardiopulmonary examination was normal. Her abdomen was nontender and without hepatosplenomegaly. Her strength was 2 out of 5 in proximal and distal legs, bilaterally, and 4 out of 5 in proximal and distal upper extremities. She had normal muscle tone without fasciculations or atrophy. Her joints were without edema, erythema, or impaired range of motion. She had normal sensation to light touch in arms and legs. Her reflexes were 2+ in the patellar, Achilles, and brachioradialis tendons. She had no lymphadenopathy, mucosal ulcerations, or alopecia. A skin examination revealed smooth, slightly elevated, and faded pink wheals that were diffuse but most prominent in upper arms and chest.

Physical examination confirms the presence of true muscle weakness. The differential diagnosis is narrowed by several findings, both positive and negative, elicited in the examination. The diffuse nature of the weakness eliminates focal central nervous system lesions, such as stroke, intracranial mass lesions, or demyelinating white matter foci. Combining this finding with normal reflexes and history of preceding myalgias makes electrolyte-induced and inflammatory (eg, polymyositis) myopathies more likely. The normal deep tendon reflexes and the absence of a delayed relaxation phase lower the likelihood of hypothyroidism.