To present a case of Cryptococcus gattii meningoencephalitis in an immunocompetent adult which was subsequently complicated by the development of anti-LGI1 encephalitis.

Cryptococcus gattii is an emerging fungal pathogen that is being increasingly recognized as a cause of meningitis and/or meningoencephalitis in immunocompetent patients without HIV infection. Anti-LGI1 encephalitis is an autoimmune limbic encephalitis that typically presenting with seizure, memory disturbance, and psychiatric symptoms, primarily in older male patients . There has been no published report of Cryptococcus gattii meningnitis associated with LGI1-antibody encephalitis.

A 68-year-old male with a history of hypertension presented with a one-month history of progressive headaches, personality changes, and irritability. MRI brain demonstrated mild microvascular ischemic changes and was otherwise normal. Cerebrospinal fluid (CSF) analysis revealed lymphocytic pleocytosis (230 cells/µL), elevated protein (226 mg/dL), low glucose (15 mg/dL), positive CSF cryptococcal antigen screening at high titer (1:2560), and growth of Cryptococcus gattii on fungal cultures. The patient was initiated on anti-fungal treatment and initially showed clinical improvement. However, approximately one week later, the patient’s cognitive status deteriorated. A repeat MRI brain demonstrated left medial temporal lobe T2/FLAIR hyperintensities without associated enhancement. Video electroencephalogram (EEG) monitoring revealed suspected faciobrachial dystonic seizures without electrographic correlate. Ultimately, autoantibody testing was positive for LGI1 antibodies by cell-based assay in both serum (titer 1:160) and CSF (titer 1:10). The patient was subsequently treated with high-dose steroids and intravenous immunoglobulin for anti-LGI1 encephalitis with significant neurological improvement.

To our knowledge, this is the first report of anti-LGI1 encephalitis associated with cryptococcal meningitis. This case highlights the importance of considering parainfectious autoimmune encephalitis in patients with neurological infections who fail to appropriately respond to antimicrobial therapy. It also highlights the emergence of Cryptococcus gattii as an important cause of neurological infection in otherwise immunocompetent patients without HIV.