Skin and muscle lesions of nine patients with clinically and histologically typical dermatomyositis were studied for the paramyxovirus-like inclusions previously described in several other connective tissue and autoimmune diseases. The detection rate of the inclusions correlated well with the degree of disease activity. The inclusions were cytoplasmic in small vessels of the skin lesion and could also be perinuclear in large vessels of the muscle. Tubules composing the inclusion budded from the wall of the endoplasmic reticulum or from nuclear membrane. No budding through the plasma membrane was observed. Uranyl acetate used in tissue block staining increased the tubular density and ribonuclease disintegrated, though not completely, the tubules. An increased number of lysosomes in the inclusion-positive cells was associated with the vascular damage. Tissue culture studies and serological tests for several paramyxoviruses were negative.
Hashimoto K, Robison L, Velayos E, Niizuma K. DermatomyositisElectron Microscopic, Immunologic, and Tissue Culture Studies of Paramyxovirus-Like Inclusions. Arch Dermatol. 1971;103(2):120–135. doi:10.1001/archderm.1971.04000140006003