To highlight an approach to diagnosis of complex autoimmune disorders with multineuraxial involvement by reviewing the case of a 50-year-old male with ptosis and bulbar weakness, REM behavior disorders, and extrapyramidal involvement, diagnosed with anti-IGLON5 disease.

Anti-IGLON5 disease is a relatively novel autoimmune neurological disorder, with its first case reported in 2014. Prevalence being only 12 out of 150,000 patients per year, this disorder is characterized by sleep abnormalities, movement disorders, bulbar symptoms, and cognitive impairment. The condition is often misdiagnosed due to its variable presentation and overlap with other neurodegenerative and autoimmune disorders.

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A 50-year-old male from western India presented with history of sleep disturbances characterized by vivid dreams, sleep talking, dream enactment, along with asymmetric ptosis and bulbar involvement. On account of ptosis and bulbar symptoms, he was misdiagnosed as a case of myasthenia gravis, with a close differential of motor neurone disease, for which he received treatment. Over time, he developed a myriad of hyperkinetic movement disorders, including cervical and auricular dystonia, perioral dyskinesias, and blepharospasm with mild cognitive impairment in the form of episodic memory loss. Hence, a possibility of autoimmune encephalitis was considered. MRI Brain was normal, and PET-CT was suggestive of degenerative changes. In view of the predominant burden of sleep disturbances with bulbar involvement and hyperkinetic movement disorders, anti-IGLON-5 disease was considered, and serum anti-IGLON-5 antibodies were found to be strongly positive. Treatment with pulse steroids and further immunomodulation led to improvement of his IGLON-5 composite score from 24 to 19 over a follow-up period of 3 months. 

Anti-IGLON5 disease should be considered in patients presenting with REM behavior disorders with bulbar symptoms and movement disorders. The complex phenotype can mimic myasthenia gravis or motor neurone disease. Clinical suspicion and early testing can lead to accurate diagnosis with timely immunosuppressive treatment.