Hypereosinophilic Syndrome Subtype Predicts Responsiveness to Glucocorticoids

Background: Glucocorticoids (GCs) are considered first-line treatment for platelet-derived growth factor α (PDGFRA)-negative hypereosinophilic syndromes (HESs). Despite this, little is known about clinical predictors of GC responsiveness in HES.

Objective: Knowledge of clinical and laboratory predictors of GC response before initiation of GC could lead to more rational selection of subjects with HES for whom earlier institution of second-line and alternative therapies would be appropriate.

Methods: Response to GC, as defined by the reduction of the absolute eosinophil count to below 1000/mm and control of symptoms, was assessed by a retrospective chart review of subjects with PDGFRA-negative HES evaluated on an institutional review board-approved protocol. Demographic, clinical, and laboratory parameters obtained before institution of GC, as well as final diagnosis, were evaluated to determine predictors of GC response. Proportional odds models were used for univariate and multivariate assessment of predictors with permutation adjusted P values to correct for multiple comparisons.

Results: A total of 164 subjects with PDGFRA-negative HES were categorized according to GC response. Of them, 39% of the subjects responded to low dose (≤10 mg) prednisone, 9% did not respond to GC, and the remainder (52%) had variable responses to GC. The HES subtype diagnosis was the best predictor of response to GC with myeloid forms and lymphocytic variants of HES being the least responsive to GC.

Conclusions: In a large cohort of well-characterized subjects with HES, the odds of response to GC was predicted by HES subtype. Using this model, clinicians may more readily proceed to second-line agents in subjects with confirmed lymphocytic or myeloid forms of HES.