Pseudo-Chediak-Higashi anomaly in a case of acute myeloid leukemia: electron microscopic studies.

The formation and fine structure of giant granules in neutrophil promyelocytes of a patient with a variant of acute myelogenous leukemia were investigated by electron microscopy. The patient presented with large lymph nodes and disseminated intravascular coagulation (DIC). By light microscopy, numerous giant granules, resembling those of Chediak-Higashi syndrome (CHS), were present, but Auer bodies could not be found. By electron microscopy, these giant granules were seen to be formed by fusion of azurophilic granules, as in CHS; however, they were different from the large granules of CHS, since they contained numerous microcrystalline structures like those of Auer bodies. However, the crystalline cores of these granules exhibited a periodicity different from that of Auer bodies of acute promyelocytic leukemia. This clinical and hematologic syndrome (giant granules, enlarged lymph nodes, and DIC may represent a variant of acute promyelocytic leukemia.