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Characteristics in limbic encephalitis with anti-adenylate kinase 5 autoantibodies
Le-Duy Do1, Eve Chanson1, Virginie Desestret1
1From the French Reference Center on Paraneoplastic Neurological Syndrome (L.-D.D., E.C., V.D., B.J., F.D., V.R., J.-Y.D., J.-C.A., J.H.) and Service de Neurologie D (V.D., M.F.), Hôpital Neurologique, Hospices Civils de Lyon; Institut NeuroMyoGene INSERM U1217/CNRS UMR 5310 (L.-D.D., E.C., V.D., B.J., F.D., V.R., J.-Y.D., J.-C.A., J.H.), Université de Lyon-Université Claude Bernard Lyon 1; Université Grenoble Alpes (S.B., Y.C.), CEA, iRTSV-BGE, Inserm 1038, Grenoble; EA 3082 (C.T.-A.), Université Lyon 2, France; Service of Neurology (L.B.), Hospital Universitario Fundación Alcorcón, Madrid, Spain; Service de Neurologie (B.L., F.T.), CHU Bordeaux and UMR CNRS 5293 Université de Bordeaux; Unité de Neurologie Cognitive, Epilepsie et Pathologie du Mouvement (J.C.), Explorations Fonctionnelles Neurologiques, Hôpital Pierre Paul Riquet, Toulouse; Service de Neurologie (T.D.B.), Hopital Delafontaine, Saint-Denis; Neurology (C.L.-F.), University Hospital Pasteur 2, Nice; Département de Neurologie (J.-Y.D.), Groupe Hospitalier Pitié-Salpêtrière, Paris; and Neurology Department (J.-C.A.), CHU Saint-Etienne, France.
Objective:
To report 10 patients with limbic encephalitis (LE) and adenylate kinase 5 autoantibodies (AK5-Abs).
Methods:
We conducted a retrospective study in a cohort of 50 patients with LE with uncharacterized autoantibodies and identified a specific target using immunohistochemistry, Western blotting, immunoprecipitation, mass spectrometry, and cell-based assay.
Results:
AK5 (a known autoantigen of LE) was identified as the target of antibodies in the CSFs and sera of 10 patients with LE (median age 64 years; range 57-80), which was characterized by subacute anterograde amnesia without seizure and sometimes preceded by a prodromal phase of asthenia or mood disturbances. Anterograde amnesia can be isolated, but some patients also complained of prosopagnosia, paroxysmal anxiety, or abnormal behavior. No associated cancer was observed. All 10 patients had bilateral hippocampal hypersignal on a brain MRI. CSF analysis generally showed a mild pleiocytosis with elevated immunoglobulin G index and oligoclonal bands, as well as high levels of tau protein with normal concentration of Aβ42 and phospho-tau, suggesting a process of neuronal death. Except for one patient, clinical response to immunotherapy was unfavorable, with persistence of severe anterograde amnesia. Two patients evolved to severe cognitive decline. Hippocampal atrophy was observed on control brain MRI. Using in vitro tests on hippocampal neurons, we did not identify clues suggesting a direct pathogenic role of AK5-Abs.
Conclusions:
AK5-Abs should be systematically considered in aged patients with subacute anterograde amnesia. Recognition of this disorder is important to develop new treatment strategies to prevent irreversible limbic damage.
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