CalR and MPL Driver Mutations and Their Role in the Diagnosis and Clinical Course of JAK2-Unmutated Chronic Myeloproliferative Neoplasm: Results from a Pilot Single-Center Study

<i>Background and Objectives</i>: Philadelphia (Ph)-negative myeloproliferative neoplasms can exhibit defects in Janus kinase 2 (JAK2), Calreticulin (CalR), and MPL genes. It is possible that the presence of other driver mutations may influence diagnosis and prognosis in patients who do not have a JAK2 gene mutation. The purpose of this study was to assess the frequency of CalR and MPL gene mutations and the clinical effects of these mutations in JAK2 gene-unmutated MPN patients from a single center. <i>Materials and Methods</i>: We examined 46 patients (ET/PMF: 34/12) diagnosed with MPNs regarding their genetic conditions, diagnoses, and complications. <i>Results</i>: CalR Type 1 gene mutation was detected in 26.1% of cases, CalR Type 2 gene mutation in 13.0%, MPL-L gene mutation in 2.2%, and MPL-K gene mutation in 6.5%. In total, 56.5% of patients were triple-negative. The presence of CalR Type 1 and Type 2 mutations was significantly more prevalent in patients with essential thrombocytosis (ET), although the difference did not reach statistical significance (<i>p</i> = 0.51, <i>p</i> = 0.57). In contrast, MPL mutations were only observed in patients with primary myelofibrosis (PMF). <i>Conclusions</i>: We found no correlation between thrombosis, leukemic transformation, and driver mutations. MPL gene mutation was present in only myelofibrosis patients, and CALR gene mutation was present in one of the three cases of leukemic transformation. The triple-negative group had a lower survival rate, but this difference was not statistically significant (110.3 months vs. 121.4 months, respectively, <i>p</i> = 0.53). However, the sample size was quite small. Our limited observations suggest a possible trend that requires confirmation.