Objective: Describe a case of subacute parkinsonism associated with isolated Zic4 antibodies.

Background: Movement disorders are a common feature in autoimmune encephalitis and its presentation can mimic a neurodegenerative disease. In particular, adult-onset immune-mediated parkinsonism has been associated with Ri, Ma2, NMDAR, LGI1, CRMP5, and IgLON5 antibodies. The Zinc-finger protein 4 (Zic4) onconeuronal antibodies were described in paraneoplastic cerebellar degeneration, mainly in patients with small-cell lung carcinoma.

Method: A case report.

Results: A 77-year-old woman presented with a two-month history of gait impairment, postural instability, mental slowness, and weight loss of 20 kg. Other reported symptoms included nausea, anorexia, dysphagia to liquids, and shouting during sleep. Her examination revealed facial hypomimia, speech slurring, mild appendicular rigidity, mild appendicular bradykinesia, moderate global slowing, inability to arise from the chair without help, small step gait and severe postural instability requiring unilateral assistance. Aside from saccade hypometria, there were no other cerebellar signs in the neurological examination. General blood work, brain MRI, EEG, and CSF analysis were unremarkable. The search of anti-neuronal antibodies in blood and CSF revealed positivity for serum Zic4 antibodies (confirmed by immunodot and immunofluorescence). Screening for occult cancer with abdominal CT, colonoscopy, and esophagogastroduodenoscopy was negative. Thoracic CT revealed nonspecific micronodules in the right lower lung lobe, and therefore a PET scan was requested. While waiting for the workup results, the patient started a trial of levodopa up to 400mg with no response. With the diagnostic suspicion of immune-mediated parkinsonism, the patient started treatment with intravenous high-dose methylprednisolone (1 g/day for 5 days). On the last day, there was a slight improvement, mainly in the axial signs: the patient was able to push herself from the arms of the chair, there was an improvement in the postural stability, and the gait was now independent but with substantial impairment.

Conclusion: Although the clinical significance of Zic4 antibodies is still unclear, most reported cases presented with subacute cerebellar syndrome. To our knowledge, this is the first case described in the literature of a subacute parkinsonism associated with Zic4 antibodies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subacute-parkinsonism-associated-with-zic4-antibodies-a-case-report/