In particular, the observation that only 16,7% of CALR-mutated patients show a reduction in CALR allele burden after Ruxolitinib treatment27 suggest that the hyperactivation of the JAK2-STAT5 signaling pathway downstream MPL might not be the only pathogenetic mechanism in CALR-mediated MPN development. This evidence concerns the gene MPL and myeloproliferative neoplasm.