Diagnostic algorithm in chronic myeloproliferative diseases (CMPD)

The Philadelphia-negative chronic myeloproliferative diseases (CMPD) are very complex and heterogeneous disorders. They are represented by polycythemia vera (PV), chronic idiopathic myelofibrosis (CIMF), essential thrombocythemia (ET), CMPD/unclassifiable (CMPD-U), chronic neutrophilic leukemia (CNL), and chronic eosinophilic leukemia/hypereosinophilic syndrome (CEL/HES) according to the WHO classification. Before, diagnostics were mainly focused on clinical and morphological aspects, but in recent years cytogenetics and fluorescence in situ hybridization (FISH) found entrance in routine schedules as chromosomal abnormalities are relevant for prognosis and classification. Recently, there is rapid progress in the field of molecular characterization: the JAK2V617F mutation which shows a high incidence in PV, CIMF, and ET already plays a central role and will probably soon be included in follow-up procedures. Due to the detection of mutations in exon 12 of the JAK2 gene or mutations in the MPL gene the variety of activating mutations in the CMPD is still increasing. In CEL/HES the detection of the FIP1L1-PDGFRA fusion gene and overexpression of PDGFRA and PDGFRB led to targeted therapy with tyrosine kinase inhibitors. Thus, diagnostics in the CMPD transform toward a multimodal diagnostic concept based on a combination of methods -cyto-/histomorphology, cytogenetics, and individual molecular methods which can be included in a diagnostic algorithm.