These results reinforce the hypothesis that the FIP1L1/PDGFRA gene fusion and D816V-KIT mutation cause distinct clinical syndromes.     ///    " The broad and overlapping clinical manifestations of D816V KIT-associated systemic mastocytosis with eosinophilia and FIP1L1/PDGFRA-associated chronic eosinophilic leukemia (CEL), coupled with the increase in activated eosinophils and mast cells seen in both disorders, have led to confusion in the nomenclature. "    ///    "Thirty-four FIP1L1/PDGFRA-positive patients described in the literature were also classified using this system, and although a complete set of data was not available for any of the historical patients, 21 were correctly classified. "    ///    We compared 12 patients with D816V-positive systemic mastocytosis with eosinophilia with 17 patients with FIP1L1/PDGFRA-positive CEL.     ///    This system correctly classified 16 of 17 FIP1L1/PDGFRA-positive patients with CEL and all 12 patients with systemic mastocytosis with eosinophilia.     ///    KIT D816V-associated systemic mastocytosis with eosinophilia and FIP1L1/PDGFRA-associated chronic eosinophilic leukemia are distinct entities.. 