Charcot–Leyden crystals in myeloproliferative neoplasm with <scp>ETV6</scp>‐<scp>ABL1</scp> and t(7;8)

Charcot-Leyden crystals in myeloproliferative neoplasm with ETV6-ABL1 and t(7;8)A 51-year-old male patient experienced shortness of breath following physical activity.The full blood count showed a leucocytosis (376.70 10 9 /L) and anaemia (68 g/L).Manual differential count showed 2% myeloblasts, 4% eosinophils and 7% basophils.The bone marrow aspirate demonstrated significant hyperplasia of the granulocyte series, where eosinophils constituted 9% and basophils 6%.Localised necrosis was present, along with a substantial number of bipyramidal crystals, identified as Charcot-Leyden crystals (CLCs) (Wright stain, objective 100; images, upper left, middle, right panels, lower left and middle panels).Flow cytometry analysis revealed 2.23% myeloid blasts.The BCR-ABL gene was not detected, but testing for ETV6/ABL1 gene was positive.Cytogenetic analysis exhibited an abnormal karyotype 46,XY,t(7,8)(q22;q13)[8]/46,XY[12] (cytogenetic panel lower right).After symptomatic treatment, the patient received oral nilotinib, and after 3-year follow-up, molecular testing did not demonstrate ETV6/ABL.A large number of CLCs were observed in this case.CLCs are customarily detected in haematological malignancies