Chronic Eosinophilic Leukemia (CEL) is a rare subtype of HES. CEL is associated with consistently increased eosinophil counts in the blood, bone marrow, and tissue. It occurs most often in middle-aged adults, particularly in men (9:1 versus women).
Symptoms are similar to those mentioned previously for all myeloproliferative neoplasms, but may also include:
- Central nervous system irregularities
- Congestive heart failure
- Pulmonary fibrosis
- Peripheral vasculitis
- Heart/lung damage from eosinophilic granule release (a frequent cause of death for CEL patients)
Eosinophils account for 30-70% of the WBCs in the peripheral blood; blasts do not exceed 20%. WBC counts are usually greater than 30 x 109
/L. Specific cytogenetic abnormalities have been noted, but are rare, in CEL. Bone marrow fibrosis is common.
Since this condition can mimic secondary eosinophilia or other neoplastic disorders with eosinophil involvement, the clonality of the eosinophils should be demonstrated to diagnose the category of hypereosinophilic syndrome containing the CEL diagnosis. In addition, all other possible causes of eosinophilia should be ruled out. Additional tests that may be ordered to confirm a CEL diagnosis are:
- Vitamin B12 (increased in CEL)
- Tryptase (increased in CEL)
- Interleukin 5 (normal levels in CEL
- Uric acid (increased in CEL)
- Muramidase (increased in CEL)
- Evaluation for the FIP1L1-PDGFRA fusion gene.
Treatment protocols for patients with CEL have included chemotherapy medications such as hydroxyurea, busulfan, 6-thioguanine, cyclophosphamide, vincristine, corticosteroids, and interferon-α. In addition, anti-IL-5 antibody therapy has recently been suggested for CEL treatment. Allogeneic stem cell transplantation has also been utilized.