Pseudo-Chediak-Higashi anomaly in acute myeloid leukemia (M2) of childhood.

The frequency and clinical significance of the pseudo-Chediak-Higashi (PCH) anomaly were studied in 20 children with acute myeloid leukemia (AML) M2 in the FAB nomenclature. PCH granules were recognized as giant eosinophilic granules, measuring up to 5 microns, in the cytoplasm of leukemic cells on smears. At the electron microscope level, most PCH granules were round to oval and outlined by a limiting membrane, and contained homogeneous, granular, crystalloid, rod-like or myelin-like materials. The PCH anomaly was demonstrable in five (25.0%) of the 20 patients, which indicates that the anomaly is not rare in childhood AML M2. There were no differences between PCH anomaly-positive and PCH anomaly-negative groups with regard to hepatosplenomegaly, hemoglobin levels, white blood cell counts, bone marrow cellularity, t(8q-, 21q+) chromosome abnormalities or prognoses. Circulating leukemic cells were observed less frequently in the PCH anomaly-positive group than in the PCH anomaly-negative group (p less than 0.05); the leukemic cells were not demonstrable in three of the five patients in the former group, although they were detected in all 15 patients in the latter group. The existence of PCH granules and/or a defect of the cytoskeleton responsible for the PCH anomaly in leukemic cells may impede their movement from the bone marrow to the peripheral blood.