Rapid and robust reversion to essential thrombocythemia on treatment with Decitabine in a case of hydroxyurea-induced t-MDS/AML

Rapid remission of MDS/AML may be induced with Decitabine; however, significant megakaryocyte expansion and subsequent thrombocytosis may occur. Decitabine‐mediated reversion of the MDS to benign ET via hypomethylation of JAK/STAT pathway repressors is one potential mechanism to explain this observed phenomenon.

Calreticulin (CALR) mutation in myeloproliferative neoplasms (MPNs)

As a heterogeneous group of disease, myeloproliferative neoplasms (MPNs) have confused hematologists and hematopathologists with their protean clinical presentations and myriads of morphologies. A thought of classifying MPNs based on molecular alterations has gained popularity because there is increasing evidence that molecular or chromosomal alterations have a better correlation with clinical presentation, response to therapies, and prognosis than conventional morphological classification. This type of efforts has been facilitated by the advancement of molecular technologies. A significant number of gene mutations have been identified in MPNs with JAK2 and MPL being the major ones. However, a significant gap is present in that many cases of MPNs do not harbor any of these mutations. This gap is recently filled by the discovery of Calreticulin (CALR) mutation in MPNs without JAK2 or MPL mutation and since then, the clinical and molecular correlation in MPNs has become a hot research topic. There seems to be a fairly consistent correlation between CALR mutation and certain hematological parameters such as a high platelet count and a better prognosis in MPNs with CALR mutation. However, controversies are present regarding the risks of thrombosis, interactions of CALR with other gene mutation, the role of CALR in the pathogenesis, and the optimal treatment strategies. In addition, there are many questions remain to be answered, which all boiled down to the molecular mechanisms by which CALR causes or contributes to MPNs. Here, we summarized current published literatures on CALR mutations in MPNs with an emphasis on the clinical-molecular correlation. We also discussed the controversies and questions remain to be answered.

CALR mutations screening in wild type JAK2(V617F) and MPL(W515K/L) Brazilian myeloproliferative neoplasm patients

Some myeloproliferative neoplasm (MPN) patients harbor JAK2(V617F) mutation, and CALR mutations were recently discovered in wild type (WT) JAK2(V617F). We evaluated the frequency and type of CALR mutations, and clinical and hematological characteristics in WT JAK2(V617F) and MPL(W515K/L) MPN patients. Sixty-five patients were included: 21 with primary myelofibrosis (PMF), 21 with myelofibrosis post-essential thrombocythemia (MPET) and 23 with essential thrombocythemia (ET). Screening for JAK2(V617F) and MPL(W515K/L) were performed using real-time PCR, while CALR mutations were analyzed by fragment analysis and Sanger sequencing. JAK2(V617F) was the most frequent mutation (54.5%) and one patient (1.5%) harbored MPL(W515L). CALR mutations were present in 38.1% of PMF, 12.5% of ET and 33.3% of MPET patients. Five types of CALR mutations were detected, among which type 1 (32.1%) and type 2 (21.4%) were found to be the most common. A novel CALR mutation in a PMF patient was found. Patients carrying CALR mutations had higher platelet count and less presence of splenomegaly than JAK2(V617F), while triple negatives had higher C-reactive protein levels than CALR mutant carriers. Screening for CALR mutations and its correlation with clinical features could be useful for the characterization of MPN patients and result in its incorporation into a new prognostic score.