paraneoplastic encephalomyelitis
Summary
An immune-mediated CNS syndrome triggered by an underlying tumor (classically small cell lung cancer) via anti-Hu (ANNA-1) antibodies. Causes subacute multifocal neurologic deficits, often preceding the cancer diagnosis.
Detail
Tumor antigens shared with neurons induce cross-reactive T cells and autoantibodies, leading to neuronal injury. The classic association is small cell lung cancer with anti-Hu (ANNA-1) antibodies, which target HuD nuclear protein in neurons; it can produce limbic encephalitis, sensory neuronopathy, cerebellar degeneration, brainstem encephalitis, or autonomic dysfunction in any combination. Other antibody-tumor pairs: anti-Yo (PCA-1) -> ovarian/breast cancer with cerebellar degeneration; anti-Ma2 -> testicular cancer with limbic/brainstem encephalitis; anti-NMDA receptor -> ovarian teratoma with psychiatric symptoms and seizures. CSF shows lymphocytic pleocytosis and oligoclonal bands; MRI may show T2 hyperintensities in limbic structures. Treatment is identification/treatment of the tumor plus immunotherapy (steroids, IVIG, plasmapheresis); response is often limited because damage is T-cell mediated.
Sources
- First Aid for USMLE Step 1 2024
- Robbins Basic Pathology 10th ed
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.