Eosinophilia-Myalgia Syndrome Workup
- Author: Thomas A Medsger, Jr, MD; Chief Editor: Herbert S Diamond, MD more...
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Because the presenting symptoms and physical findings in eosinophilia-myalgia syndrome (EMS) vary significantly, the workup is mainly directed toward identifying other possible causes of the patient's findings. Laboratory tests are essential in differentiating EMS from other causes of myalgia, weakness, and eosinophilia.
The presence of peripheral blood eosinophilia is an essential element in the diagnosis of EMS based on the CDC surveillance criteria. This finding may be missed because eosinophilia occurs early in the course of the disease and may later disappear spontaneously.
- Even though the CDC criteria require an eosinophil count of at least 1000 cells/µL for diagnosis, the eosinophil counts observed in EMS patients are most frequently higher.
- Eosinophil counts of 10,000-30,000 cells/µL are not unusual, and the bone marrow shows hyperplasia of eosinophil precursor cells.
Laboratory findings commonly observed in patients with EMS include the following:
- Leukocytosis: White blood cell count elevations may range from mild to moderate.
- Abnormal LFT results are common, and mild-to-moderate elevation of transaminase levels is observed in approximately 40% of patients. Frank liver failure has not been described.
- An elevated serum creatine kinase level is uncommon, affecting only approximately 10% of patients with EMS. levels that are below normal are more common. Elevated aldolase levels are common and occur in approximately half of patients.
- Mild-to-moderate elevation of the erythrocyte sedimentation rate (ESR) is observed in one third of patients. ESRs greater than 50 mm/h are infrequent.
- Antinuclear antibodies with a speckled pattern in low titer are observed in approximately half of patients. The significance of this finding is uncertain.
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Chest radiographic results vary from normal to acute infiltrates.
Pleural effusion and infiltrates (diffuse or bibasilar) are seen in less than one third of patients.
MRI of the brain has shown subcortical infarcts, focal lesions in the deep white matter, cortical atrophy, ventricular dilatation, and both diffuse and periventricular white matter abnormalities.
MR spectroscopic findings are consistent with widespread inflammatory cerebrovascular disease.
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Pulmonary function testing reveals a slightly decreased diffusion capacity in up to half of patients with EMS but no evidence of restrictive lung disease.
Electrophysiologic studies demonstrate myopathic and neuropathic changes of varying degrees. Nerve conduction studies show mixed demyelination and a pattern of axonal degeneration.
Echocardiography typically shows normal left ventricular function and estimated pulmonary artery (PA) pressure less than 30 mm Hg, but pulmonary arterial hypertension is occasionally detected.
Biopsy of skin muscle and/or subcutaneous tissue
No consistent findings are observed in biopsy specimens from patients with EMS; therefore, histopathologic findings are helpful but not diagnostic.
Muscle biopsy commonly reveals inflammatory infiltrates, frequently perivascular, in the endomysium and perimysium. The inflammatory cells are predominantly lymphocytes and acid phosphatase–reactive histiocytes, with rare eosinophils. In some instances, microangiopathy is present. Generalized type II myofiber atrophy and denervation atrophy are common, but myofiber necrosis and degeneration are infrequent.
Skin/fascia biopsy findings generally reveal a normal epidermis. The dermis may be normal or may have perivascular infiltrates of monocytes, eosinophils, and lymphocytes without fibrinoid necrosis. Fasciitis is indistinguishable from eosinophilic fasciitis. Findings vary from extensive infiltrates with lymphoplasmacytoid cells, eosinophils, and monocytes to diffuse fibrosis of connective tissue extending into dermis and epimysium. These findings differ from those in patients with scleroderma, who have more collagen deposition in the dermis.
Nerve biopsy shows a combination of demyelination and axonal degeneration, with epineural, perineural, and perivascular cellular infiltrates.
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