James M. Powers

Mycoplasmas, particularly Mycoplasma pneumoniae, have been implicated as causative agents in a large variety of central nervous system diseases, especially acute childhood encephalitis. Postulated pathomechanisms for mycoplasma-mediated neurological disease have included: direct infection, autoimmunity, and vascular occlusion. Neuropathologic data are meager and are reviewed. We report a 3-year-old boy, who developed signs and symptoms of encephalitis 7 days after the onset of fever with cough and death 5 days later. At autopsy, he displayed diffuse vasogenic edema and perivascular to infiltrative inflammatory cells, the latter most prominent in gray matter of brainstem and amygdala. The predominant cell was the CD68-positive macrophage, followed by the T-lymphocyte. Cells immunolabeled with a polyclonal antibody to M. pneumoniae included perivascular to parenchymal macrophages/microglia, occasional oligodendrocytes, and neurons, particularly in brainstem. Affected neurons varied from morphologically normal to profoundly degenerate and necrotic. Ultrastructural study of the inferior olive confirmed the presence of 260–600 nm cell-wall-free microorganisms, consistent with mycoplasma, in perivascular cells and neurons. Foci of acute disseminated encephalomyelitis also were rarely identified. This case report confirms the postulated role of direct infection of brain by mycoplasma in acute childhood encephalitis, but also reveals a virus-like infection of central neurons. The pathogenesis of acute childhood encephalitis due to mycoplasma seems to be multifactorial.

Eosinophilic inclusions in the cytoplasm of protoplasmic astrocytes of the neocortex, usually in the clinical setting of epilepsy and/or psychomotor retardation, were first recognized and illustrated by Alois Alzheimer in 1910. Traditional special stains have failed to elucidate the specific nature of these inclusions. Ultrastructurally, the material was composed predominantly of highly electron-dense, non-membrane-bound, granular material distinct from Rosenthal fibers. Immunohistochemical examination has been informative but also sometimes inconsistent; it has recently been suggested that they may represent a filaminopathy (filamin A). We examined 5 cases with neocortical eosinophilic inclusions (3 autopsies, 2 surgical resections) using a standardized immunohistochemical protocol at a single institution. The specimens were immunostained with 32 antibodies to 30 potentially relevant proteins using several antigen retrieval protocols. We confirmed the presence of filamin A in these inclusions, but several additional proteins, particularly cytoglobin and glutamate transporter 1, were also identified. By electron microscopy in 2 cases, the granular fine structure of the inclusions was confirmed; mitochondria adjacent to, and perhaps within, the inclusions that contained many pleomorphic vesicular and membranous elements were also noted in 1 case. The pathophysiologic relevance of these proteins and the clinical significance of the hyaline inclusions are discussed.

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 disease, and 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.

We performed a blinded study on 5 cases of hereditary diffuse leukoencephalopathy with spheroids and 10 cases of the pigmentary type of orthochromatic leukodystrophy, 6 of the latter having a family history of neurologic illness. Patients presented in the third to sixth decade with behavioral, cognitive, and motor symptoms. All cases displayed widespread myelin loss, predominantly frontotemporal with relative sparing of subcortical U-fibers, and variable numbers of both neuroaxonal spheroids and pigmented glia. Immunohistochemically, spheroids contained amyloid precursor/neurofilament proteins, several neurotransmitters or neuropeptides, and ubiquitin. Cytoplasmic inclusions in glia and numerous pigmented macrophages were autofluorescent and stained consistently with diastase-periodic acid-Schiff, prolonged Ziehl-Nielsen, and Sudan black, but the same cells labeled inconsistently for iron or ferritin. Ultrastructurally, the most characteristic autofluorescent glial lipopigments consisted of bosselated masses of granular, electron-dense material. These morphologic features are those of ceroid, an end-product of oxidative damage. Glial immunoreactivity for markers of oxidative stress (hemeoxygenase-1 and superoxide dismutase 2) and damage (4-hydroxynonenal, malondialdehyde, and nitrotyrosine) was noted, particularly in cases with increased iron and ferritin. These data support the hypothesis that the similar clinicopathologic features of hereditary diffuse leukoencephalopathy with spheroids and the pigmentary type of orthochromatic leukodystrophy reflect a common disease due, at least in part, to an oxidative insult.

The apoptotic death of putaminal neurons and glia in a patient with hereditary ferritinopathy is studied immunohistochemically with antibodies to p53, activated caspase-3, PUMA, BAX, cytochrome c, and inducible nitric oxide synthase. In addition to the overexpression of ferritin and the iron accumulations assumed to result from the genetically incompetent ferritin molecule, additional contributions to the iron, heme, and hyaline deposits in this disease are sought with antibodies to 2 recently discovered globins in humans, neuroglobin and cytoglobin. The "pathognomonic" swollen to vacuolated nuclei are immunoreactive for both p53 and activated caspase-3, indicating the intervention of the p53-mediated apoptotic pathway. The immunohistochemical demonstration of neuroglobin in the swollen nuclei and both globins in the hyaline deposits highlights the potential pathogenic importance of 2 other iron-containing proteins in this disease that is largely restricted to brain. Hereditary ferritinopathy is the first human disease in which abnormalities in these heme-containing proteins are demonstrated.

We report a family of French Canadian and Dutch ancestry with hereditary ferritinopathy (neuroferritinopathy) and a novel mutation (C insertion at nt646-647 in exon 4) in the ferritin light chain gene, resulting in a longer than normal protein. Our failure to immunostain most of the abnormal ferritin deposits in the proband with a conformation-dependent monoclonal antibody to ferritin light chain supported a previously postulated conformational change of ferritin light chain in this disease. The posterior putamen and cerebellum were the primary pathologic loci in our proband, but asymptomatic hepatocytic intranuclear accumulations of iron and ferritin also were present. Both neurons and glia displayed highly distinctive, if not pathognomonic, swollen to vacuolated nuclei containing ferritin and iron. Hyaline deposits, again staining for both ferritin and iron, were additional morphologic features that may be unique to the ferritinopathies. The iron, at least in putamen where there was a nearly 40-fold increase, appeared to be both in the ferrous (Fe²⁺) and ferric (Fe³⁺) form; it was the most likely cause of the observed neuronal and glial apoptosis. We found morphologic evidence of both lipid peroxidation and abnormal nitration of proteins in putaminal neurons and glia, confirming the expected oxidative stress due to this excessive iron. Biochemical and immunohistochemical abnormalities in mitochondria also were demonstrated, probably due to an imbalance in iron homeostasis that had a deleterious effect on the respiratory chain.