Caspr2 antibody limbic encephalitis is associated with Hashimoto thyroiditis and thymoma

Area of Science:

• Neuroimmunology
• Neurology
• Endocrinology

Background:

• Contactin-associated protein 2 (Caspr2) antibodies are neuronal surface antibodies (NSAbs) implicated in central and peripheral nervous system disorders.
• Thymoma is a known comorbidity in Caspr2 antibody-associated syndromes, often presenting with peripheral nervous system symptoms.
• Hashimoto thyroiditis (HT) has not been previously reported in association with Caspr2 antibody-associated syndromes.

Observation:

• A 76-year-old woman presented with subacute cognitive decline.
• Investigations revealed the presence of thymoma and co-existing Hashimoto thyroiditis.
• Caspr2 antibody was detected in serum but not cerebrospinal fluid (CSF).

Findings:

• Brain MRI showed diffuse cortical atrophy, and PET revealed widespread cerebral hypometabolism.
• Despite treatment including corticosteroids, azathioprine, plasmapheresis, and thymectomy, cognitive status improved only partially.
• The patient's neurological presentation was attributed to Caspr2 antibody-associated limbic encephalitis.

Implications:

• This case demonstrates that thymoma-associated limbic encephalitis can occur with Caspr2 antibodies, and Hashimoto thyroiditis may be an accompanying condition.
• Neuroimaging findings like MRI and PET may not reveal specific limbic lesions in these patients.
• Patients with Caspr2 antibodies, thymoma, and associated autoimmune conditions may have a guarded prognosis.