Aplastic anemia followed by leukemia in congenital trisomy 8 mosaicism. Ultrastructural studies of polymorphonuclear cells in peripheral blood.

The case of a 40-year-old patient with congenital trisomy 8 and sex chromosome mosaicism is discussed. The main clinical features were: mental retardation, thick and darkly pigmented skin, prominent forehead, convergent strabismus, high arched palate, flexion contractures of the extremities, and numerous skeletal abnormalities. The patient developed severe aplastic anemia followed by an interim period of preleukemia which developed into acute leukemia. Electron microscope examination of the white blood cells at the stage of the aplastic anemia showed ultrastructural abnormalities similar to those observed in other genetic disorders with a predisposition to leukemia, as well as in leukemia.