biostudies-literatureKluin-Nelemans HCAustrian Science Fund FWFDeutsche Forschungsgemeinschaft1090-1101https://www.ebi.ac.uk/biostudies/studies/S-EPMC7115841biostudies-literatureUnknown34(4)Systemic mastocytosis (SM) is frequently associated with eosinophilia. To examine its prevalence and clinical impact in all WHO classification-based subcategories, we analyzed eosinophil counts in 2350 mastocytosis patients using the dataset of the European Competence Network on Mastocytosis. Ninety percent of patients had normal eosinophil counts, 6.8% mild eosinophilia (0.5-1.5 × 10⁹/l), and 3.1% hypereosinophilia (HE; >1.5 × 10⁹/l). Eosinophilia/HE were mainly present in patients with advanced SM (17%/19%), and only rarely recorded in patients with indolent and smoldering SM (5%/1%), and some patients with cutaneous mastocytosis. The eosinophil count correlated with organomegaly, dysmyelopoiesis, and the WHO classification, but not with mediator-related symptoms orLeukemiaPrognostic impact of eosinophils in mastocytosis: analysis of 2350 patients collected in the ECNM Registry.PMC7115841F 4701RA2838F 4704Shoumariyeh KZanotti RBreynaert CPanse JNiedoszytko MMattsson MElena CRossignol JJawhar MScaffidi LNiederwieser DFortina ABJakob TPerkins CDoubek MLortholary OParente RValent PGorska AVarkonyi JSabato VIllerhaus ALange MKilbertus AArock MAberer EGotlib JHagglund HHermine OZink AHartmann Kvon Bubnoff NBonadonna PTriggiani MSchwaab Jvan Anrooij BCaroppo FKennedy VYavuz ASReiter ABrockow KFuchs DSperr WRSpan LFRMalcovati LKluin-Nelemans HCfalsePrognostic impact of eosinophils in mastocytosis: analysis of 2350 patients collected in the ECNM Registry.Systemic mastocytosis (SM) is frequently associated with eosinophilia. To examine its prevalence and clinical impact in all WHO classification-based subcategories, we analyzed eosinophil counts in 2350 mastocytosis patients using the dataset of the European Competence Network on Mastocytosis. Ninety percent of patients had normal eosinophil counts, 6.8% mild eosinophilia (0.5-1.5 × 10⁹/l), and 3.1% hypereosinophilia (HE; >1.5 × 10⁹/l). Eosinophilia/HE were mainly present in patients with advanced SM (17%/19%), and only rarely recorded in patients with indolent and smoldering SM (5%/1%), and some patients with cutaneous mastocytosis. The eosinophil count correlated with organomegaly, dysmyelopoiesis, and the WHO classification, but not with mediator-related symptoms or2020-01-01T00:00:00Z2020 Apr2025-04-21T20:14:23.521Z2020-09-17T07:08:11ZS-EPMC71158413174081110.1038/s41375-019-0632-4