Adenylate kinase 5 (AK5) autoimmune encephalitis: Clinical presentations and outcomes in three new patients

Adenylate kinase 5 (AK5) antibodies are biomarkers of a poorly responsive to immunotherapy, nonparaneoplastic, autoimmune limbic encephalitis. We detected 6 patients (all female, median age: 72 years [49-80]) with identical CSF antibody staining by indirect immunofluorescence on mouse tissues. We identified AK5 as the antigen and confirmed with standardized assays. Three patients with clinical information had limbic encephalitis, inflammatory CSF and mesiotemporal lobe T2 hyperintensities that evolved to atrophy on brain MRI. One patient had burning smell sensation with no evidence of seizures. Despite immunotherapy, minimal improvement was noticed in one patient; all had severe memory deficits remaining.

Automated summary

AK5 antibodies are biomarkers of a non-paraneoplastic, autoimmune limbic encephalitis that poorly responds to immunotherapy. We identified 6 patients with the same CSF antibody staining and confirmed AK5 as the antigen. Patients presented with clinical symptoms of limbic encephalitis, inflammatory CSF, and mesiotemporal lobe abnormalities on brain MRI. Despite immunotherapy, only one patient showed minimal improvement while all others had severe memory deficits.