Myeloid Neoplasma with Eosinophilia (MLN-Eo) with Rearrangement of FGFR1 D72.1, C47.5

Myeloid neoplasms with eosinophilia are a clinically, morphologically, genetically, and prognostically heterogeneous group of clonal diseases characterized as follows:

• Initially, a persistent proliferation of clonal eosinophilic granulocytes in the peripheral blood.
• a hypercellular bone marrow
• if necessary, splenomegaly (Valent Pet al. 2012).

In morphology, the assessment of qualitative and quantitative changes in the non-eosinophil series (megakaryocytes, monocytes, mast cells, blasts) and bone marrow fibrosis is significant. By means of molecular genetic investigations, cytogenetic aberrations (e.g. reciprocal translocation, deletion, inversion, trisomy, complex karyotype), rearrangements of genes (FISH analysis), fusion genes (FISH analysis, RT-PCR) or mutations (allele-specific PCR, NGS) are included in the diagnosis. The causative genetic aberrations are characterized by a varying risk of progression to a myeloid or lymphoid blast phase (with a corresponding unfavorable prognosis).

Note: In myeloid neoplasia with eosinophilia (MLN-Eo) with rearrangement of FGFR1, about 14 different partner genes of FGFR1 have now been identified (Verstovsek S et al. (2018).

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Clinically, patients often present with primary blast phase or rapid transition to secondary blast phase, of lymphoid or myeloid origin, sometimes also extramedullary. The clinical course of MLN-Eo with FGFR1 fusion gene is aggressive, the time to transformation into blast phase or secondary acute leukemia is usually only 1-2 years. Patients often develop an extramedullary manifestation.

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