Inclusion body myositis: Electron microscopy study of 9 cases

On routine examination of 266 muscle biopsies by histology, histochemistry and transmission electron microscopy, we diagnosed 9 cases of inclusion body myositis (IBM). We analyzed all the ultrastructural features present in these cases as to the pre-dictability of them in diagnosing IBM. All 9 cases shared common transmission electron microscopy features, such as: intranuclear filaments (Fig. 1), filaments within muscle fibers (Fig. 2), membranous whorls (rimmed vacuoles), cytoplasmic bodies (Fig. 3), mitochondrial accumulation and paracrystalline inclusions (Fig. A), honeycomb structures (Fig. 5), and atrophic fibers (Fig 6).266 muscle biopsies were studied. The biopsy was obtained by using the convential muscle clamp in all the cases. After getting the muscle biopsy in each case, about 1/3 of the length was frozen in liquid nitrogen at -170 degrees F to be used for histochemistry. The second 1/3 was fixed in formalin for paraffin section, and the remaining 1/3 was minced in small pieces and fixed in 2.5% glutaraldehyde for electron microscopy study.