To describe the clinical features, diagnostic process, and outcome of three anti-GABA_A receptor (GABA_AR) encephalitis cases in patients with a history of autologous stem cell transplant (aSCT) for multiple myeloma (MM).

The relationship between aSCT for MM and anti-GABA_AR encephalitis is unknown.

A case series of 3 patients. Anti-GABA_AR antibody was tested at the University of Pennsylvania laboratory.

Patients were all male, with ages at onset of 52, 61, and 62, and time from aSCT to encephalitis symptom onset 9 months, 18 months, and 3 years, respectively. One patient also had a past medical history of prostate cancer treated 6 years prior with brachytherapy. All three cases presented with new seizures. Other symptoms included headache, visual obscurations, dizziness, and altered cognitive function in 2 cases, and anosmia and mania in one case. Brain magnetic resonance imaging (MRI) demonstrated multifocal T2 hyperintensities involving gray and white matter without contrast enhancement in all three patients. Two patients underwent brain biopsy before initiating therapy, which demonstrated non-specific encephalitis with astrogliosis in the white matter; these two patients were started on immunotherapy after 25 days and 14 weeks. One case was started on empiric immunotherapy within 8 days of the presentation without a brain biopsy. Cerebrospinal fluid (CSF) analysis revealed anti-GABA_A antibodies in all three cases. All patients recovered to work full-time within one year.

We highlight the importance of considering anti-GABA_AR encephalitis in patients with seizures and characteristic multifocal, non-enhancing brain lesions involving gray and white matter on brain MRI. Awareness in recovered post-aSCT MM patients may be crucial as prompt recognition can avoid brain biopsy. Rapid initiation of immunotherapy while awaiting autoantibody results likely increases positive functional outcomes.