However, when a patient presents with isolated thrombocytosis and a positive JAK2V617F assay, particularly a young woman, the possibility of PV must always be considered because of plasma volume expansion.
Investigation for polycythaemia and thrombocytosis showed JAK2 positive myeloproliferative neoplasm.A diagnosis of AOP infarction is often missed or delayed because it is rare and presents with variable neurological symptoms.
These observations of our case raise two possibilities: either transient posttreatment thrombocythemia is a feature of AML with JAK2V617F mutation, or this was a case of secondary AML.
Thrombocytosis can be due to genetic alterations that affect either the intrinsic MPL signaling through gain-of-function (GOF) activity (<i>MPL, JAK2, CALR</i>) and loss-of-function (LOF) activity of negative regulators (<i>CBL, LNK</i>) or the extrinsic MPL signaling by <i>THPO</i> GOF mutations leading to increased TPO synthesis.
We investigated the JAK2V617F, CALR and STAT5 activation status in patients with CML and thrombocytosis (CML-T) that mimicked ET, trying to identify a common mechanism for thrombocytosis in MPN.
The identification of somatic calreticulin (CALR) mutations can be used to confirm the diagnosis of a myeloproliferative disorder in Philadelphia chromosome-negative, JAK2 and MPL wild type patients with thrombocytosis.
Time free from cytoreduction was significantly shorter in CALR-mutated patients with essential thrombocythemia than in JAK2(V617F)-mutated ones (median time 5 years and 9.8 years, respectively; P=0.0002) and cytoreduction was usually necessary to control extreme thrombocytosis.
Recently, germline mutations in Janus kinase 2 (JAK2) and MPL, two genes frequently mutated in sporadic MPD, have been shown to cause inherited thrombocytosis.
We propose that JAK2 and MPL expression levels regulate megakaryocytic proliferation vs differentiation in both normal and pathological conditions, and that JAK2 chemical inhibitors could promote a paradoxical thrombocytosis when used at suboptimal doses.
Refractory anemia with ring sideroblasts (RARS-T) associated with marked thrombocytosis is a myelodysplastic/myeloproliferative neoplasm associated with both SF3B1 and JAK2 or MPL mutations.
Age, JAK2(V617F) and SF3B1 mutations are the main predicting factors for survival in refractory anaemia with ring sideroblasts and marked thrombocytosis.
In light of the findings from previous reports, screening for the JAK2-V617F mutation should be considered for any Ph(+) CML patients with thrombocytosis, leukocytosis, or erythrocytosis at diagnosis and for patients who subsequently develop thrombocytosis, leukocytosis, or erythrocytosis during follow-up, even for CML patients in complete cytogenetic response and major molecular response.
Given their diagnostic relevance, it is also beneficial and relatively straightforward to screen JAK2V617F negative patients for JAK2 exon 12 mutations (in the case of erythrocytosis) or MPL exon 10 mutations (thrombocytosis or myelofibrosis) using appropriate assays.
In the case of a patient with erythrocytosis and other signs of myeloproliferation, such as leukocytosis, thrombocytosis or splenomegaly, the diagnosis of polycythemia vera (PV) is likely, and I test serum erythropoietin and JAK2 mutations first.
Further investigations for intracoronary thrombus with no underlying atherosclerotic disease revealed positive Janus kinase 2 (JAK2) V617F gene mutation, and this was consistent with a diagnosis of ET with elevated platelet count.
More studies are needed to prove the role of JAK2 in ineffective erythropoiesis, iron metabolism and thrombocytosis and to determine if using JAK2 inhibitors in thalassemic patients can be a potential therapeutic option.
These data also support the hypothesis that level of JAK2(V617F) expression influences the MPN phenotype: higher levels favor erythrocytosis whereas lower levels favor thrombocytosis.
JAK2(V617F) was identified in 9 of 15 cases, including 7 of 9 with thrombocytosis (platelet count, >600 × 10(3)/μL [600 × 10(9)/L]) and 1 with 8% ring sideroblasts.
A 66-year-old man who presented with progressive and marked thrombocytosis but normal hemoglobin was diagnosed to have essential thrombocythemia upon the demonstration of JAK2V617F mutation.