Résumé
We report the ultrastructural abnormalities of the leukocyte granules and the cytogenetic findings in a patient of Chediak-Higashi syndrome (CHS), who presented with cutaneous melanosis as the only clinical feature. The diagnosis of CHS was established by peripheral smear and bone marrow examination. Chediak-Higashi syndrome, a rare autosomal recessive disorder is characterized by enlarged abnormal organelles in leukocytes and other cells. An interesting aspect of our patient was the absence of recurrent infections or any other clinical stigmata. Ultrastructurally, the leukocytes and their precursors in the bone marrow showed characteristic homogenous and heterogenous giant inclusions of variable sizes and shapes. These represent the primary granules which enlarge to attain the giant abnormal size by fusion with other primary or secondary granules. Cytogenic study of the bone marrow cells showed monosomy of chromosomes 8 and 17 in 20 percent of the metaphases. Neither the gene nor the chromosomal abnormalities specific for CHS have been identified as yet and thus the significance of our cytogenetic finding is presently not clear.