Acute actinomycotic brain abscess in a patient with rheumatoid arthritis.

An autopsy case of acute actinomycotic brain abscess involving a patient with rheumatoid arthritis (RA) is reported. The patient was a 72-year-old man with a seven-year history of RA and pulmonary complications, who acutely developed dysarthria and dysphagia three days before death. Autopsy revealed a fresh, non-encapsulated abscess in the "late cerebritis" stage, measuring 2 cm in diameter, in the white matter of the right parietal lobe. A small number of tiny "sulfur granules" consisting of numerous filamentous bacilli were found within the abscess. The abscess had ruptured to the lateral ventricle and elicited ventriculitis, and mild acute purulent leptomeningitis was also observed. The lung showed chronic interstitial pneumonia/pulmonary fibrosis with bronchiectasis and emphysema, and large sulfur granules were found in the lumens of a few bronchi. Less than 5% of patients with actinomycotic infection develop central nervous system lesions, and actinomycotic brain abscesses make up only 0.6% of all brain abscesses. Actinomycotic brain abscesses usually pursue a protracted clinical course, and well-formed pyogenic membranes are commonly observed. The present case is exceptional in that the very early stage of the cerebral abscess formation was pathologically captured.