Ultrastructural observations on the cells of a patient with Fanconi's anemia transforming to acute leukemia.

: The ultrastructural findings in the bone marrow and peripheral blood cells of a patient with Fanconi's anemia transforming to acute myelo-monocytic leukemia are presented. They consisted of an unusual large number of nuclear pockets, bridges and appendices observed in the nuclei of the polymorphonuclear cells, monocytes and to a lesser extent in the mature normoblasts. Since the mother and two younger brothers of the propositus were found to have macrocytic anemia and pancytopenia, most probably Fanconi's anemia, their peripheral blood cells were also examined with the electron microscope. The cells of all of them showed similar nuclear alterations, although in lesser quantity. The possibility that these findings are consistent with the diagnosis of Fanconi's anemia, or they herald an evolution of the disease to acute leukemia is considered.