[[Eosinophil]]ic [[phenotype]]s in [[polycythemia vera]] (PV) and [[essential thrombocythemia]] (ET) are rare and poorly characterized. Co-occuring [[JAK2 mutation]]s in [[cis]], specifically both [[L611S]] or [[N622Y]] [[mutation]]s, appear to result in a more aggressive clinical [[phenotype]]. PV/ET with eosinophilic phenotypes may require full next generation sequencing to capture co-occurring mutations as opposed to more prevalent single gene assays. These eosinophilic phenotypes are highly thrombotic and systemic symptoms appear responsive to early use of the janus kinase (JAK) inhibitor [[Ruxolitinib]]
((Patel A, Juskevicius R, Mohan S. Novel JAK2 Exon 14 Mutations L611S And N622Y in cis with JAK2 V617F Are Associated with Distinct Clinical Phenotype of Polycythemia Vera and Concurrent Eosinophilia. Acta Haematol. 2022 Nov 3. doi: 10.1159/000527695. Epub ahead of print. PMID: 36327906.)).