CALR mutations screening in wild type JAK2V617F and MPLW515K/L Brazilian myeloproliferative neoplasm patients

Some myeloproliferative neoplasm (MPN) patients harbor JAK2V617F mutation, and CALR mutations were recently discovered in wild type (WT) JAK2V617F. We evaluated the frequency and type of CALR mutations, and clinical and hematological characteristics in WT JAK2V617F and MPLW515K/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 JAK2V617F and MPLW515K/L were performed using real-time PCR, while CALR mutations were analyzed by fragment analysis and Sanger sequencing. JAK2V617F was the most frequent mutation (54.5%) and one patient (1.5%) harbored MPLW515L. 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 JAK2V617F, 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.