PT - JOURNAL ARTICLE AU - Amélia Soraia Andrade Pita AU - Ana Paula da Silva Azevedo AU - Alice Reichert AU - Cândido José Pimenta da Silva AU - Vanessa Henriques AU - Diana Sousa Mendes AU - Ana Maria Batalha Reis AU - Rita Cerqueira AU - Fátima Torres AU - João Faro Viana TI - Atypical haematological presentation in a case of polycythaemia vera with a new variant mutation detected in exon 12: c.1605G>T (p.Met535Ile) AID - 10.1136/jclinpath-2017-204556 DP - 2017 Oct 11 TA - Journal of Clinical Pathology PG - jclinpath-2017-204556 4099 - http://jcp.bmj.com/content/early/2017/10/11/jclinpath-2017-204556.short 4100 - http://jcp.bmj.com/content/early/2017/10/11/jclinpath-2017-204556.full AB - One of the major genetic insights into the pathogenesis of polycythaemia vera included the identification of the somatic point gain-of-function mutations in Janus kinase 2 gene—first JAK2V617F on exon 14, present in 95%–97% of the cases, and later on exon 12. In the literature, we can find some reported studies where different exon 12 mutations are identified. Unlike patients with JAK2V617F mutation in exon 14, the mutation at exon 12 is not usually associated with an increase in the three haematopoietic series (erythrocytosis, leucocytosis and thrombocytosis). It appears to be associated with a distinct syndrome, mostly characterised by isolated and more marked erythrocytosis, independently of the mutational variant. We report here the case of a patient who is JAK2exon 12 positive, presenting a novel mutation—c.1605G>T (p.Met535Ile)—associated with c.1612C>T (p.His538Tyr) mutation previously described, evidencing an atypical clinical phenotype.