Steroid-responsive inflammatory leptomeningeal encephalitis temporally associated with lecanemab therapy: A case report.

Authors

Yuichiro Tagane, Masahiro Nakamori, Marina Ishida, Saya Tsuchigauchi, Takamichi Sugimoto, Yu Yamazaki, Hirofumi Maruyama

Published in

Journal of Alzheimer's disease reports. Volume 10. Pages 25424823261483284. Epub Sep 09, 2026.

Abstract

Lecanemab is an anti-amyloid-β monoclonal antibody used for the treatment of early Alzheimer's disease. Herein, we report a 46-year-old woman who developed headache, fever, disorientation, and impaired consciousness 10 months after starting lecanemab. Magnetic resonance imaging revealed a small focal subcortical fluid-attenuated inversion recovery hyperintense lesion and bilateral occipital leptomeningeal enhancement without detectable hemorrhagic findings on T2*-weighted gradient-recalled echo imaging. Cerebrospinal fluid revealed mononuclear pleocytosis and markedly elevated interleukin-6. Infectious studies and neuronal surface antibodies were negative. High-dose corticosteroid therapy led to rapid clinical improvement. These findings support a diagnosis of steroid-responsive inflammatory leptomeningeal encephalitis temporally associated with lecanemab.

PMID:
42876904
Bibliographic data and abstract were imported from PubMed on 15 Oct 2026.

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