Autoimmune atypical parkinsonism — A group of treatable parkinsonism

• This article defines a treatable subset of atypical parkinsonism.
• Characterized by atypical parkinsonism with neuronal specific antibodies.
• Sometimes associated with abnormal CSF.
• Significant and prompt response to immunotherapy.

BackgroundImmunological causes of atypical parkinsonism/Parkinson plus syndromes are rare.ObjectiveTo study the clinical and laboratory features and treatment outcome of autoimmune atypical parkinsonism.MethodsRetrospective case series. Patients with atypical parkinsonism and positive antibodies were identified retrospectively. Those who received immunotherapy (intravenous methyl prednisolone 1 g daily for five days followed by mycophenylate mofetil 2 g daily or azathioprine 2–3 mg/kg/day) and consented for publication of non-anonymized videos were included.ResultsThere were ten cases (nine males, age range 49–75 years, disease duration 2 months to 13 years, follow-up 1–7 months) of atypical parkinsonism [probable multiple system atrophy (MSA)-2, possible progressive supranuclear palsy (PSP)-1, probable PSP-3]. Eight had new uncharacterized neuronal antibodies, leucine rich glioma associated protein 1 (LGI1) antibody in one, and the other had another uncharacterized neuronal antibody along with LGI1 antibody. Four had abnormal CSF. There was a prompt, dramatic improvement in terms of Unified Parkinson Disease Rating Scale motor scale and or modified Rankin Scale as well as improvement in eye movement, postural instability, cerebellar, autonomic and non-motor symptoms. Two had reappearance of symptoms on discontinuing steroids and improvement on restarting. One died of infection despite good recovery of encephalopathy and parkinsonism.ConclusionAutoimmune atypical parkinsonism is characterized by atypical parkinsonism with neuronal specific antibodies, sometimes associated with abnormal CSF and significant response to immunotherapy.