To describe a case of Kelch-like protein 11 (KLHL11) antibody-associated rhombencephalitis presenting with progressive ophthalmoplegia and other brainstem and cerebellar features.

KLHL11 antibody, first identified in 2019, defines a rare paraneoplastic neurological syndrome associated with testicular cancer. This disorder, KLHL11 antibody-associated rhombencephalitis, typically presents with ataxia, diplopia, vertigo, sensorineural hearing loss, and dysarthria, although recognition of additional cases has revealed a broader clinical spectrum.

A 57-year-old male with a remote history of testicular cancer status post left orchiectomy presented to the clinic with a chief complaint of diplopia. He retrospectively recalled symptoms beginning one year earlier, including subtle limb incoordination, followed by intermittent diplopia that progressed to constant diplopia, partially relieved by prism lenses. Additional symptoms included personality changes, mood swings, headaches, hypophonia, dysarthria, gustatory lacrimation, and rhinorrhea. Prior evaluation attributed his symptoms to hypofunctioning vestibular dysfunction, supported by videonystagmography. Balance therapy provided partial improvement, but gait instability and unsteadiness persisted. Physical exam demonstrated bilateral ophthalmoparesis, bilateral dysmetria, dysdiadochokinesia, and wide-based unsteady gait. Neuroimaging was notable for cerebellar atrophy and patchy pontine hyperintensities. Serum autoimmune encephalopathy panel at a tertiary center was positive for KLHL11 antibodies with a titer of 1>7680, confirming the diagnosis of KLHL11 antibody-associated rhombencephalitis. Aggressive immunotherapy with several rounds of intravenous methylprednisolone and cyclophosphamide were initiated with no disease progression to date. 

KLHL11 antibody-associated rhombencephalitis should be considered in men presenting with subacute ocular motor and cerebellar syndromes, even years after tumor resection. Careful history-taking and thorough evaluation can help identify subtle prodromal features and expedite diagnosis. Currently, there is no cure for this disease; however, treatment is aimed at halting progression to improve quality of life, a goal that was achieved in this patient.