Insights from response to tyrosine kinase inhibitor therapy in a rare myeloproliferative neoplasm with CALR mutation and BCR-ABL1.

To the editor: Calreticulin ( CALR ) mutations have been reported primarily in the context of JAK2 and MPL wild-type essential thrombocythemia and primary myelofibrosis.[1][1][⇓][2][⇓][3][⇓][4]-[5][5] CALR mutations are exceedingly rare in the setting of t(9;22)/ BCR-ABL1 ,[4][4],[5][5] with