Ultrastructural localization of histones in chronic erythremic myelosis.

The localization of histones was studied ultrastructurally with the use of the ammoniacal silver stain in erythroid precursors from 6 patients with chronic erythremic myelosis (Di Guglielmo syndrome), 3 patients with severe untreated pernicious anemia, 2 patients with untreated autoimmune hemolytic anemia, and 4 presumedly normal individuals. Silver deposits, indicative of sites of arginine-rich histone within nuclei, were not observed in proerythroblasts from any of the individuals. Small deposits of silver were seen in the heterochromatin in very early intermediate normoblasts. Differences in the amount and distribution of the silver deposits in the various types of erythroid precursors first became recognizable in the intermediate normoblast stage. In all of the individuals, the silver deposits were localized predominantly in the heterochromatic regions of the nucleus. In 6 patients with chronic erythremic myelosis, unusually, dense deposits of silver were observed in erythroid precursors having amounts of heterochromatin comparable to that found in intermediate normoblasts of intermediate megaloblasts in other conditions. In these chronic erythremic myelosis erythroid precursors, the silver deposits were larger and, in many instances, appeared to be more aggregated than in erythroid precursors obtained from 3 patients with untreated pernicious anemia, 2 patients with autoimmune hemolytic anemia, and 4 presumedly normal persons. It is possible that the findings described in this study are involved in the pathogenesis of megaloblastoid erythropoiesis as found in chronic erythremic myelosis.