Pediatric Hypereosinophilic Syndrome Workup

Updated: Aug 02, 2018
  • Author: Bruce M Rothschild, MD; Chief Editor: Harumi Jyonouchi, MD  more...
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Laboratory Studies

Hypereosinophilic syndrome is characterized by an eosinophil count of more than 1500/μL (usually many more).

It is necessary to evaluate for a 4q12 microdeletion (800 kb) that produces recombination fusion, forming the FIP1L1/PDGFRA fusion gene. [8, 9] The formation of the FIP1L1/PDGFRA fusion gene results in increased tyrosine kinase activity of PDGFRA, rendering poor response to steroids but sensitivity to imatinib. [10]

The erythrocyte sedimentation rate (ESR) is usually elevated but can be normal. Leukocyte alkaline phosphatase levels may be high or low. Hypergammaglobulinemia in the form of extremely high immunoglobulin E (IgE) levels is noted in one third of patients. Immunoglobulin G (IgG), immunoglobulin M (IgM), and immunoglobulin A (IgA) levels are only rarely elevated.

Rheumatoid factor is only rarely present. Coombs test may be positive. Results of rapid plasma reagin (RPR) tests are rarely positive. Hematuria, proteinuria, and azotemia may be present. Synovial fluid eosinophilia is prominent.

Chromosomal analysis rarely reveals abnormalities. When abnormal chromosomes are present, a workup for eosinophilic leukemia is recommended. Eosinophilic leukemia is an unrelated disorder. The presence of chromosome abnormalities or eosinophil blast cells in the circulating blood or marrow may allow the leukemia to be recognized.

A laboratory workup is also indicated to rule out disorders that can mimic the hypereosinophilic syndrome (see Differentials).


Imaging Studies

Chest radiography may reveal nonspecific focal or diffuse, interstitial, or alveolar infiltrates. CT scanning may reveal pulmonary nodules with a halo of ground-glass attenuation, as well as nonspecific focal or diffuse, interstitial, or alveolar infiltrates. Ultrasonography findings of the affected liver may be normal. Technetium-99m sulfur colloid scanning may reveal nonhomogenous uptake in the presence of liver disease.


Other Tests

Electrocardiography may reveal atrial fibrillation, ST-segment depression, T-wave changes, conduction abnormalities, left atrial atrophy, or left ventricular hypertrophy. Electrocardiography reveals cardiac involvement in 90% of patients with hypereosinophilic syndrome.



Bone marrow biopsy may reveal myelofibrosis. The presence of eosinophil blast cells suggests the alternative diagnosis of eosinophilic leukemia, an unrelated disorder.


Histologic Findings

Activated eosinophil levels are noted in the blood and involved structures; this finding is associated with fibrosis.