NTRK1 and hypereosinophilic syndrome: Within the United States, the estimated occurrence ranged from 0.36 to 6.3 cases per 100 000 individuals.1 While several subtypes of HES demonstrate an equitable distribution across genders, HES associated with genetic anomalies affecting the tyrosine kinase receptors platelet-derived growth factor receptor alpha (PDGFRA) and platelet-derived growth factor receptor beta [PDGFRB] exhibit a discernible male predominance.