Laboratory Studies
Complete blood cell count with differential
By definition, patients should have an eosinophil count higher than 1.0 X 109 cells/L.
A value of 1.5 X 109 cells/L is suggested as an alternate baseline value, with more weight given to eosinophil counts higher than 3 X 109 cells/L.
An elevated white blood cell count is observed in 46% of patients and is often secondary to the eosinophilia.
Liver function tests
Abnormal results of liver function tests are observed in 43% of patients with EMS.
These abnormalities can include elevated levels of bilirubin, alanine transaminase, aspartate transaminase, alkaline phosphatase, and gamma-glutamyl transferase.
Creatine kinase and aldolase tests
Levels are elevated in 3% of patients with EMS.
Major basic protein and eosinophil-derived neurotoxin tests
Serum levels of major basic protein are 213-1352 ng/mL (reference range, 158±42), and urine levels are 9-225 ng/nL (reference range, 10±10).
Serum levels of eosinophil-derived neurotoxin are 10-208 ng/mL (reference range, 16±6), and urine levels are 113-10,700 ng/nL (reference range, 298±145).
Immunologic workup
This set of tests is important to rule out other known rheumatologic diseases, such as scleroderma.
Patients with EMS may have an elevated antinuclear antibody titer, but, generally, anti-Ro, anti-La, antiribonucleoprotein (anti-RNP), anticentromere, anti-DNA, Smith antigen, and Scl-70 results are negative. One patient with EMS had elevated antimitochondrial antibody levels.
Imaging Studies
Chest radiography
Chest radiographic findings may be normal, even in patients with evidence of lung function compromise.
Abnormal findings may include basilar interstitial opacities, lower lobe infiltrates, diffuse interstitial infiltrates, pleural effusions, and reticulonodular infiltrates.
Head MRI
Head MRIs may show several areas of increased signal intensity in the white matter and the corpus callosum, particularly in the occipital region.
MRIs may also reveal focal areas of increased signal intensity in the parietal lobe.
Abdominal CT
Abdominal CT scans may show splenomegaly in 1% of patients with EMS.
Hepatomegaly is found in 5% of patients with EMS.
Other Tests
Electromyography
Electromyography (EMG) shows evidence of myopathy in two thirds of patients.
In many cases of EMS, EMG reveals evidence of polyneuropathy that is often severe. This finding is consistent with demyelination and associated axonal involvement.
Pulmonary function tests
The results of pulmonary function tests (PFTs) are abnormal in patients with respiratory symptoms and in some patients without respiratory symptoms and normal chest radiographic findings.
PFTs demonstrate both mild-to-moderate obstructive lung disease and restrictive lung disease.
Forced vital capacity, forced expiratory volume in 1 second, total lung capacity, and single-breath carbon monoxide diffusing capacity values are diminished in patients with EMS.
Electrocardiography
ECG findings are usually normal.
Reported abnormalities include atrial flutter, left-axis deviation with a pattern of right ventricular strain, minor ventricular and atrioventricular delays, right ventricular hypertrophy, and poor R-wave progression across the precordium with no acute ST- or T-wave changes.
Echocardiography
Echocardiograms may show a moderate pericardial effusion, an enlarged right ventricle with decreased function, or a thickened mitral valve.
Echocardiograms may show cor pulmonale with tricuspid regurgitation in patients with pulmonary hypertension.
Histologic Findings
Biopsy samples of the skin and the underlying fascia reveal the following characteristic findings: thickening of the fascia with homogenization of collagen accompanied by an inflammatory cell infiltrate in the fascia, subcutaneous adipose tissue, interlobular septa, and deep reticular dermis. This infiltrate is primarily composed of lymphocytes, but eosinophils and plasma cells are also found.
Biopsy samples of the muscle reveals prominent findings in the endomysium, the perimysium, and the fascia that consist of a perivascular and interstitial inflammatory infiltrate composed of lymphocytes, histiocytes, plasma cells, and rare eosinophils.
Histopathologic features in the nervous tissue may include perivascular, perineural, epineural, or endoneural inflammation with mononuclear cells with or without eosinophils, in addition to axonal degeneration.
Histologic findings in the lung may show perivascular inflammation, interstitial inflammation with or without fibrosis, and alveolar exudate.
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Indurated edematous plaques on a patient with hypereosinophilic syndrome.
