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Inclusion body myositis (IBM) has been viewed as a distinct and rare form of inflammatory myopathy. Previously reported findings from series of IBM patients have suggested that clinical and pathologic features are present which readily distinguish it from idiopathic polymyositis. We report 4 cases of IBM presenting clinically and pathologically as polymyositis, each of which was refractory to therapy. Our data suggest that IBM may be a more common and heterogeneous form of inflammatory myopathy than has been previously suggested. Furthermore, IBM may be clinically and electrophysiologically indistinguishable from polymyositis. Reasons for failing to recognize IBM by pathologic studies appear to include: the skip lesion nature of the pathologic findings, failure to examine tissues by electron microscopy, and a low level of suspicion or lack of recognition. Because of its insidious clinical course and its failure to respond to immunosuppressive therapy, IBM may be an important variant of treatment-resistant polymyositis.

Two siblings with congenital granule cell hypoplasia of the cerebellum and hippocampus are reported. The patients, both male, showed severe psychomotor retardation, microcephaly, hypotonia, athetosis, and seizures; they died at the ages of 3 7/12 years and 5 10/12 years, respectively. Postmortem examinations in both cases revealed nearly complete absence of the granule cells of the cerebellum with relative preservation of the Purkinje cells. Also absent were the granule cells of the fascia dentata of the Ammon's horns of the hippocampus, without any detectable gliosis; this has not previously been reported. Twenty-three autopsy cases of granuloprival cerebellar hypoplasia are reviewed. The present cases illustrate a singularly unique disease process, comparable to the classical cerebellar hypoplasia experimentally induced by parvoviruses, and suggest a granule cell specific insult to the brain during the late second trimester.

Degenerated brain tissue obtained from a deceased patient who had progressive multifocal leukoencephalopathy had been fixed in formalin prior to processing for electron microscopy. In ultrathin sections virus-like particles resembling papova virions were frequently observed in glial nuclei. Correlation with light-microscopy findings suggests that demyelination resulted from the cytocidal effect of the virus on oligodendroglia.

Intranuclear and intracytoplasmic aggregates of filaments with tubular structures and transverse striations occurred in muscle tissues biopsied from a patient with chronic polymyositis. The filamentous tubules bear a close resemblance to the incomplete form of myxovirus in which the envelope is missing. Three biopsies from the same patient, taken during a period of 1(1/2) years, all revealed these structures. This finding provides presumptive evidence that a chronic persistent viral infection may be involved in the pathogenesis of chronic polymyositis.