Acute myeloid leukemia with pseudo-chédiak-higashi anomaly exhibits a specific immunophenotype with CD2 expression

Acute myeloid leukemia (AML) with pseudo–Chediak-Higashi (PCH) anomaly is a rare morphologic entity. We characterized 5 cases by multiparameter flow cytometry and found that in all cases, the blasts aberrantly expressed CD2, a pan–T cell–associated marker, in addition to their myeloidassociated markers. In contrast, CD2 was expressed in only 25 (17.9%) of 140 cases of newly diagnosed AML without PCH anomaly. CD2 expression correlated strongly with AML with PCH anomaly (P < .01), suggesting a link between a specific immunophenotypic marker, CD2, and AML with PCH anomaly. Chediak-Higashi syndrome is a rare autosomal recessive disorder characterized by increased fusion of cytoplasmic granules and cellular dysfunction. The morphologic hallmark of this disorder is the presence of giant granules in neutrophil, lymphocyte, and monocyte cytoplasm. Similar large pink or purple cytoplasmic granules, defined as pseudo-Chediak-Higashi (PCH) anomaly, have been described in rare cases of acute myeloid leukemia (AML). 1-5 These giant granules are azurophilic and myeloperoxidase-positive. Electron microscopy demonstrated small vesicles in the cytoplasm near the giant granules, 6 suggesting the granules may be formed by the fusion of primary granules and/or the fusion of small, dense vesicles.