Anti-KLHL11 antibody encephalitis without detectable malignancy: a case report and literature review.

Background: Anti-Kelch-like protein 11 (KLHL11) antibody encephalitis, first reported in 2019, is a rare autoimmune disorder typically associated with seminoma. This disorder exhibits a striking male predominance, with cerebellar ataxia as the hallmark manifestation, whereas seizures and altered consciousness occur less frequently. Cases without detectable malignancy account for fewer than 20% of reports, and their clinical manifestations, treatment responses, and outcomes have not been systematically characterized. Methods: We report a case of a 62-year-old male with anti-KLHL11 encephalitis and no detectable malignancy, who initially presented with recurrent generalized tonic-clonic seizures (GTCS), followed by intermittent seizures and progressive neurological deterioration. A systematic search of published cases with narrative synthesis was conducted to analyze the clinical presentation, neuroimaging features, treatment responses, and outcomes of similar reported cases. Results: We analyzed 13 cases of anti-KLHL11 encephalitis without detectable malignancy. The most common clinical manifestations were ataxia (9/13), dysarthria (8/13), and gaze palsy/nystagmus (6/13). Intracranial pressure (ICP) (median: 165 mmH Conclusion: Anti-KLHL11 encephalitis without detectable malignancy cannot be reliably distinguished from tumor-positive cases based solely on clinical symptoms and neuroimaging findings. The gold standard for differential diagnosis remains comprehensive tumor screening and long-term follow-up. Extensive white matter and deep gray matter involvement, together with prominent seizures, may be more prevalent in patients without detectable malignancy, although these observations require validation in larger comparative cohorts.