Suspicious of essential thrombocythemia, genomic DNA analysis of the peripheral blood sample showed no pathogenic mutations regarding Janus kinase-2 (JAK2) V617F, JAK2 exon 12, calreticulin (CALR) exon 9, and myeloproliferative leukemia virus oncogene (MPL) W515L/K. Here, CALR is linked to essential thrombocythemia.