Ultrastructure of peripheral blood granulocytes from patients with low serum cobalamin.

Peripheral blood granulocytes from ten patients with low serum cobalamin were studied using light and electron microscopic techniques. Six patients had classic neutrophil hypersegmentation using light microscopy, but three patients had an increase in band forms and rare hypersegmented cells. The electron microscope revealed nuclear appendages consisting of nuclear stalks, rings and blebs in neutrophils from all patients regardless of the degree of hypersegmentation but not from normal controls; these did not appear to result from sectioning artifact and their formation may be interrelated. Numerous cytoplasmic empty granules were seen in neutrophils from three patients. Another three showed what appeared to be granules in the shape of water-wings under low power, but on higher power were unique mitochondria. Some disorder of the eosinophil granule centrum was seen in all patients but was extreme in four patients; lipid cytoplasmic inclusions were also seen in these four and one other patient.