An unusual case of Pisa syndrome secondary to anti-IgLon 5 disease

Pisa syndrome, characterized by lateral flexion of the trunk, is most often associated with neuroleptic use or neurodegenerative disorders like Parkinson's disease. Anti-IgLON5 disease is a rare neuroimmunological condition with overlapping features of autoimmunity and tauopathy, manifesting with sleep and cognitive disturbances, bulbar symptoms, and movement disorders. We report a 50-year-old man who presented with progressive lateral trunk flexion, head drop, dysarthria, and choreiform movements. The classic features of antiIgLon 5 disease including sleep and cognitive disturbances were absent. Serum testing confirmed strong positivity for anti-IgLON5 antibodies. Treatment with rituximab led to marked clinical improvement, with amelioration of symptoms at 24 months. This case illustrates an uncommon presentation of anti-IgLON5 disease as Pisa syndrome. Recognition of this association is important, as early immunotherapy can significantly improve outcomes in an otherwise progressive and disabling condition.