Purpose::
Anti-immunoglobulin-like cell adhesion molecule 5 (IgLON5) disease is a rare autoimmune encephalitis that shares clinical features with progressive supranuclear palsy (PSP), complicating differential diagnosis. Here, we sought to investigate whether PET imaging using [
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F
]
Florzolotau and [
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F
]
FDG could distinguish these disorders through characteristic patterns of tau deposition and cerebral glucose metabolism.
Patients and Methods::
Eleven patients with serologically confirmed anti-IgLON5 disease, 20 patients with PSP diagnosed according to the 2017 Movement Disorder Society criteria, and 40 age-matched and sex-matched healthy controls were enrolled. Participants underwent [
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Florzolotau and/or [
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FDG PET imaging. Visual interpretation and semiquantitative analyses, including voxel-based and region-of-interest approaches, were performed.
Results::
Anti-IgLON5 patients showed significant [
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F]Florzolotau binding in subcortical regions, including the midbrain, pons, caudate, putamen, and thalamus, along with additional involvement of the parietal lobe and cerebellum. PSP patients demonstrated overlapping [
18
F]Florzolotau uptake in the caudate, putamen, thalamus, midbrain, and pons, but with distinct additional binding in the frontal lobe. [
18
F]FDG PET revealed contrasting metabolic profiles: anti-IgLON5 disease was associated with diffuse cortical hypometabolism, whereas PSP showed regionally restricted hypometabolism, mainly in the frontal lobe, caudate, putamen, midbrain, and pons.
Conclusions::
We identified distinct PET signatures that can reliably differentiate anti-IgLON5 disease from PSP. The complementary application of [
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]
Florzolotau and [
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]
FDG PET imaging may provide valuable biomarkers for differential diagnosis in clinically ambiguous cases, potentially enabling timely immunotherapeutic interventions for patients with imaging patterns suggestive of anti-IgLON5 disease.