RT Journal Article SR Electronic T1 The Calreticulin gene and myeloproliferative neoplasms JF Journal of Clinical Pathology JO J Clin Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 841 OP 845 DO 10.1136/jclinpath-2016-203899 VO 69 IS 10 A1 Clinton, Aoibhinn A1 McMullin, Mary Frances YR 2016 UL http://jcp.bmj.com/content/69/10/841.abstract AB The Philadelphia negative myeloproliferative neoplasms include polycythaemia vera (PV), essential thrombocytopenia (ET) and primary myelofibrosis (PMF). Patients with these conditions were mainly thought to harbour JAK2V617F mutations or an Myeloproliferative leukaemia (MPL) substitution. In 2013, two revolutionary studies identified recurrent mutations in a gene that encodes the protein calreticulin (CALR). This mutation was detected in patients with PMF and ET with non-mutated JAK2 or MPL but was absent in patients with PV. The CALR gene encodes the calreticulin protein, which is a multifactorial protein, mainly located in the endoplasmic reticulum in chromosome 19 and regulates calcium homeostasis, chaperones and has also been implicated in multiple cellular processes including cell signalling, regulation of gene expression, cell adhesion, autoimmunity and apoptosis. Somatic 52 bp deletions and recurrent 52 bp insertion mutations in CALR were detected and all resulted in frameshift and clusters in exon 9 of the gene. This review will summarise the current knowledge on the CALR gene and mutation of the gene in pathological conditions and patient phenotypes.