Idiopathic eosinophilia associated CMML-2 with overexpression of the ETV6 gene

Charcot Leyden crystals in the bone marrow are rare and have been described in the bone marrow 1,5,11 and in the soft tissue 2 (granulocytic sarcoma); however, no consistent cytogenetic abnormality has been associated. Charcot Leyden crystals are seen in fluids and tissues with eosinophilic dominated inflammatory reactions. To date, eosinophilic associated chronic myelomonocytic leukemia (CMML-2) has not been described with Charcot Leyden crystals. Recent exciting cytogenetic associations have linked idiopathic eosinophilia to myelodysplastic and myeloproliferative syndromes and in particular certain genes (ie, PDGFRbeta ETV6 fusion, FIPIL1-PDGFRalpha fusion, and others). We describe a case of idiopathic eosinophilia with Charcot Leyden crystals associated with CMML-2 and overexpression of ETV6.