D1.347 - Biomarkers in hypereosinophilic syndrome: the second step after diagnostic algorithms

Idiopathic hypereosinophilic syndrome (I-HES) currently represents a major unmet need for all medical specialties dealing with this disease in the era of precision medicine. Despite being a relatively new clinical entity, HES already has diagnostic algorithms and effective therapies, but markers to characterise the wide variability of its clinical presentation are lacking. This study aims to evaluate a panel of possible clinical and biological markers of organ damage and disease progression in I-HES.

In this pilot prospective single-centre cohort study, we analysed clinical (age, years of disease, steroid therapy) and laboratory (absolute eosinophil count (AEC), total IgE antibodies, IgE antibodies against Staphylococcus aureus enterotoxins (SEs), serum eosinophil cationic protein (ECP), serum immunoglobulin free light chains (FLCs) k and λ) and their ratio) data obtained from 21 patients suffering from I-HES referred to the Allergy and Clinical Immunology Unit of Policlinico Universitario A. Gemelli IRCCS of Rome, Italy, from June 2023 to December 2024.

21 patients (14 males and 7 females, mean age of 53.62 years) were evaluated. The mean AEC was 3758.57 cells/µL. 17 patients were receiving treatment with > 7.5 mg of prednisone or equivalent at the time of the diagnosis. 13 patients had positive SEs, while the mean total serum IgE was 241.64 kU/L. We observed a high serum ECP value (mean 92.1 µg/L) as well as a high serum κ FLCs (mean 23.72 mg/L), while serum λ FLCs and κ/λ were normal (18.34 mg/L and 1.28, respectively). Patients with higher AEC had higher ECP levels (p < 0.05), such as higher steroid consumption (p < 0.05). In addition, we found a strong association, although not statistically significant, between high κ FLCs levels and high previous steroid use, and between high κ FLCs levels and SEs positivity.

Our results could increase the number of possible biomarkers for risk stratification in I-HES, in addition to those already described in the Literature, helping to better characterise patients suffering from this disease for a more appropriate individualised clinical management.