A case of 10-year retrograde amnesia, cognitive dysfunction, and hippocampal atrophy after limbic encephalitis associated with rickettsiosis

Organisms in the genus Rickettsia are obligately intracellular gram-negative bacilli that are transmitted to humans via hematophagous arthropod vectors, and rickettsiosis is known to cause limbic encephalitis (LE). Here, we present a case of 10-year retrograde amnesia, cognitive dysfunction, and hippocampal atrophy of the brain following LE caused by rickettsiosis. A 76-year-old woman presented to the Medical Center for Dementia for reexamination and rethinking of the diagnosis of amnesia and cognitive dysfunction. She was diagnosed with rickettsiosis by clinical view and treated with antibiotics three years ago. Head imaging showed a high signal in bilateral amygdala and hippocampus. The current test showed enlarged ventricles, suggesting brain atrophy. This case report suggests that LE caused by rickettsiosis may cause persisting memory impairment, cognitive dysfunction, and brain atrophy. Clinicians must determine appropriate treatment considering the long-term sequelae of rickettsiosis.