From the Guidelines
For a 59-year-old man with an EOS of 6.3, clinical observation and monitoring without escalation of immunosuppressive therapy is conditionally recommended if there are no other signs of disease activity, as increases in inflammation markers can be non-specific 1. This approach is based on the 2021 American College of Rheumatology/Vasculitis Foundation guideline for the management of giant cell arteritis and takayasu arteritis, which suggests that increasing immunosuppressive therapy is not warranted in the setting of increased levels of inflammation markers alone 1. Key considerations in managing this patient include:
- Monitoring of clinical and radiographic assessments for active disease
- Avoiding unnecessary escalation of immunosuppressive therapy
- Recognizing that increases in levels of inflammation markers such as erythrocyte sedimentation rate and C-reactive protein can be non-specific 1 It is crucial to weigh the risks and benefits of treatment and to prioritize a thorough evaluation to identify any underlying conditions that may be contributing to the elevated EOS, rather than immediately escalating immunosuppressive therapy.
From the Research
Eosinophilia Diagnosis and Classification
- Eosinophilia is defined as an elevation of eosinophils in the bloodstream, with a count of greater than 450-550 cells/μL 2 or an absolute count of > 500 eosinophils per mm3 of peripheral blood 3.
- The diagnosis of eosinophilia can be challenging due to its association with many disorders, including parasitic disease, allergic disease, autoimmune, connective tissue disease, rheumatologic disease, primary eosinophilia, and malignant states 2.
- Hypereosinophilia (HE) is generally defined as a peripheral blood eosinophil count greater than 1.5 × 109 /L 4.
Eosinophilia Subtypes and Treatment
- The World Health Organization endorses a semi-molecular classification scheme of disease subtypes, including myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2, and the myeloproliferative neoplasm subtype, chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) 4.
- Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophilia, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion 4.
- Treatment goals include mitigating eosinophil-mediated organ damage, with options such as imatinib for patients with rearranged PDGFRA or PDGFRB, corticosteroids for patients with lymphocyte-variant HE and HES, and hydroxyurea and interferon-α for initial treatment and steroid-refractory cases of HES 4.
- Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, was recently approved for patients with idiopathic HES, and other targeted therapies such as JAK2 and FGFR1 inhibitors are under investigation 4.
Clinical and Biological Markers
- Clinical and biological markers are essential for diagnosing and managing eosinophil-associated disorders, including hypereosinophilic syndromes (HES) 5, 6.
- These markers can help identify the underlying cause of eosinophilia, determine the disease subtype, and guide treatment decisions 5, 4, 6.
- Early therapeutic application of agents reducing eosinophil counts is usually effective in avoiding irreversible organ damage in patients with HES 6.