Eosinophilia medical therapy

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:

• Medical treatment for eosinophilia should be directed at the underlying cause (for example treating parasitic infection or malignancy).
• Eosinophilia without evidence of organ dysfunction may be observed with monitoring for evidence of organ involvement.
• Treatment of hypereosinophilic syndrome has a number of options including corticosteroids, hydroxyurea, interferon-alpha, imatinib and other tyrosine kinase inhibitors, IL-5 antibodies, and other cytotoxic and immunomodulatory agents.

• Corticosteroids are most commonly used as first line therapy. They are able to produce a rapid decrease in eosinophil counts, which is valuable if there is already evidence of organ dysfunction related to high eosinophil levels. ^[1]
  • 0.5-1mg/kg/day of prednisone (or the equivalent dose of another steroids) is the recommended starting dose. Patients with non-severe disease manifestations can start with lower doses
  • Steroids are tapered over time, with second line agents added if needed to maintain control.
  • In one study, corticosteroids were able to induce remission in 85% of patients at 1 month
• Hydroxyurea is the most commonly used second-line agent for hypereosinophilic syndrome. Typical dose range is 500mg-2g per day. Hydroxyurea acts at the level of the bone marrow to reduce production of new eosinophilis. As such it is not suitable if a rapid lowering in eosinophil levels is needed. Hydroxyurea is not usually used alone, it is most often used as an additional steroid-sparing agents.
• Interferon-alpha is also a second-line, steroid sparing agent. Use of this agent is limited by its toxicities. Interferon-alpha also has activity on lymphocytes, so it may be particularly effective in eosinophilia secondary to lymphocytic malignancies.
• Imatinib and related TKIs have shown promise in treating chronic eosinophilic leukemia due to similar molecular re-arrangements as CML. ^[2] This family of TKIs is very well tolerated. These drugs are most effective in patients who have the FIP1L1-PDGFRA rearrangement driving a clonal expansion in the bone marrow.
• Other cytotoxic agents have been used in isolated cases, but lack strong evidence
• In severe cases refractory to other therapy, stem cell transplant may be considered if the cause of the eosinophilia is a primary bone marrow process.

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