A case report of sporadic Creutzfeldt–Jakob disease presenting with progressive opsoclonus–myoclonus–ataxia-Plus (OMAS-Plus) phenotype

We report an atypical sCJD phenotype dominated by progressive dysarthria and an opsoclonus–myoclonus–ataxia-plus (OMAS-plus) phenotype, highlighting the diagnostic pitfalls relative to treatable mimics.</p> <p>A 63-year-old man presented with progressive dysarthria and bulbar symptoms suggesting myasthenia gravis, but did not improve on pyridostigmine and progressed to right-predominant hemiataxia, acral polymyoclonus, dystonia, pyramidal signs, facial palsy, and cognitive–behavioural decline.

Video-oculography showed opsoclonus, upbeat nystagmus, and abnormal saccades, raising suspicion of an immune-mediated or paraneoplastic OMAS-plus; extensive autoimmune, paraneoplastic, infectious, metabolic, and neuromuscular work-up was unrevealing, and empirical corticosteroids produced no improvement. EEG lacked periodic sharp-wave complexes and CSF 14–3-3 was negative; PRNP sequencing showed a codon 129 methionine-homozygous genotype without pathogenic mutation.