Detection of Calreticulin Exon 9 Mutations in Egyptian Patients with Persistent Thrombocytosis

Abstract

hrombocytosis is defined as elevated platelet count above 450 × 109/L; this threshold was recommended by WHO (2016) and by BCSH (2010). In most literature, for thrombocytosis to be persistent, it should be sustained for at least 3 months. The major causes of thrombocytosis can be divided into reactive and clonal thrombocytosis. Reactive causes include transient processes such as acute blood loss, acute infection or inflammation, extreme physical exertion, or other stress. Sustained forms of reactive thrombocytosis include iron deficiency, hemolytic anemia, asplenia, cancer, chronic inflammatory or infectious diseases, and rare drug reactions. Clonal thrombocytosis is typically due to a chronic MPN particularly ET and pre-PMF. These clonal disorders are associated with adverse events related to the thrombocytosis, including thrombotic, vascular and bleeding complications. Calreticulin (CALR) gene mutation is now a major criterion for establishing the diagnosis of classical myeloproliferative neoplasms (essential thrombocythemia, prefibrotic primary myelofibrosis and primary myelofibrosis). It is the second common gene mutation encountered in these disorders after JAK2 mutation as it accounts for about 25-30% of cases. Cases with CALR mutation show distinct clinical and