Kelch-like Protein-11 Encephalitis Associated With Squamous Cell Carcinoma of Unknown Origin

We report a case of Kelch-like protein-11 (KLHL11) encephalitis associated with squamous cell carcinoma (SCC) of unknown origin in the neck.A 70-year-old man, diagnosed with prurigo nodularis 4 months prior, presented with subacute-onset progressive dysarthria, imbalance, and diplopia. Neurologic examination revealed horizontal and downbeating nystagmus with lateral gaze, dysarthria, dysmetria, and hearing difficulties. Skin examination showed localized pruritus with excoriated ulcerations on the neck and proximal upper extremities. MRI of the brain revealed T2 hyperintensities in the pons and left cerebellum, and CT of the neck showed a right neck mass.Extensive workup for acquired brainstem syndromes revealed KLHL11 antibodies in both the serum and CSF, together with superimposed unclassified antibodies. The patient was diagnosed with KLHL11 encephalitis and was treated with intravenous immunoglobulin, intravenous methylprednisolone, and plasmapheresis. He underwent right neck dissection, with pathology revealing SCC of unknown origin. Subsequently, the patient received monthly IV cyclophosphamide and adjuvant radiation therapy. His clinical symptoms, including the excoriated ulcerations, improved remarkably with treatment.Our patient represents the first case of KLHL11 encephalitis associated with SCC of unknown origin in the neck, and our observations delineate a potentially novel correlation between the 2 diseases.