Electron microscopic demonstration of virus particles in hand, foot and mouth disease.

Early skin and oral mucous membrane lesions of hand, foot and mouth disease (HFMD) were biopsied and investigated by light and electron microscopy. Histology showed spongiosis, intraepidermal splits indicating beginning vesicle formation, exocytosis of lymphoid cells and macrophages, and individual necrotic keratinocytes. Electron microscopy revealed naked viruses with a mean diameter of 24 nm which were arranged in sheets in the cytoplasm. Many keratinocyte nuclei contained tonofibrils. Cellular injury ranged from slight cytoplasmic edema to keratinocyte necrosis. Some nuclei showed dissolution of the nuclear membrane and dislocation of cytoplasm into the nucleus.