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Markedly Elevated IgG Index: A Key to Differentiating Neurosyphilis from Autoimmune Limbic Encephalitis
Yui Sanpei1, Akira Hanazono1, Momoka Funasaka1
1Department of Neurology, Akita University Graduate School of Medicine, Japan.
Internal Medicine (Tokyo, Japan)
|November 27, 2024
Summary
Neurosyphilis can mimic autoimmune limbic encephalitis, presenting with rapid behavioral changes and medial temporal lobe lesions. A markedly elevated cerebrospinal fluid immunoglobulin G index can aid in diagnosing this challenging neurosyphilis presentation.
Area of Science:
- Neurology
- Infectious Diseases
- Immunology
Background:
- Neurosyphilis is a re-emerging infectious disease that can present with diverse neurological manifestations.
- Limbic encephalitis, characterized by rapid cognitive and behavioral changes, is often associated with autoimmune etiologies.
- Differentiating neurosyphilis from autoimmune limbic encephalitis can be diagnostically challenging due to overlapping clinical and radiological features.
Purpose of the Study:
- To report a case of neurosyphilis initially misdiagnosed as autoimmune limbic encephalitis.
- To highlight the diagnostic challenges posed by atypical presentations of neurosyphilis.
- To emphasize the utility of cerebrospinal fluid immunoglobulin G index in diagnosing neurosyphilis.
Main Methods:
- Case report of a 48-year-old male patient.
- Clinical assessment including behavioral changes and neurological examination.
- Magnetic Resonance Imaging (MRI) of the brain to evaluate medial temporal lobe lesions.
- Cerebrospinal fluid (CSF) analysis for abnormalities and syphilis serology.
- Serum tests for syphilis.
Main Results:
- The patient presented with rapid behavioral changes suggestive of limbic encephalitis.
- MRI revealed high-intensity lesions in both medial temporal lobes.
- CSF analysis showed abnormalities, and serum tests were positive for syphilis.
- A markedly elevated CSF immunoglobulin G index (4.91) was observed.
Conclusions:
- Neurosyphilis can present atypically, mimicking autoimmune limbic encephalitis.
- Diagnostic differentiation requires a comprehensive approach including serological and CSF analyses.
- A markedly elevated CSF immunoglobulin G index may be a crucial indicator for neurosyphilis in cases of suspected autoimmune limbic encephalitis.
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