We present 3 sporadic cases of a subacute to chronic, progressive motor (i.e. weakness, ataxia, spasticity, dysarthria, and dysphagia) and cognitive disorder in adults of both sexes, without proven immunocompromise or malignancy. Neuroimaging studies revealed tiny calcifications with atrophy of the cerebrum, pons, and midbrain in 1 patient, cerebral atrophy in another, and cerebral atrophy and periventricular white matter hyperintensities in the third. Clinical diagnoses included cortico-pontine-cerebellar degeneration, mixed neurodegenerative disorder, progressive supranuclear palsy, diffuse Lewy body
Lyme disease. One atrophic brain revealed widely disseminated, millimeter-sized gray lesions in cerebral white matter and obscured anatomic markings of the basis pontis. The most conspicuous microscopic feature in all was capillaries with focally piled up endothelial nuclei, some of which appeared to be multinucleated, or enlarged, hyperchromatic crescentic single nuclei. Although seen mostly without associated damage, they were also noted with white matter lesions displaying vacuolation, demyelination, spheroids, necrosis, vascular fibrosis, and mineralization; these were most severe in the basis pontis. Immunostains and probes to herpes simplex virus-I, -II, and -8; adenovirus, cytomegalovirus, varicella-zoster, Epstein-Barr virus, measles, JC virus, and herpes hominis virus-6 were negative. Electron microscopy revealed no virions in endothelial cells with multilobed or multiple nuclei and duplicated basal laminae. However, mycoplasma-like bodies, mostly 400 to 600 nm in size, were found in endothelial cell cytoplasm and capillary lumina. Platelets adhered to affected endothelial cells. Polymerase chain reaction and immunohistochemistry of fixed samples for Mycoplasma fermentans were negative; other species of Mycoplasma remain viable pathogenic candidates.