Nocturnal behaviours, stridor and recurrent respiratory failure in anti-IgLON5 disease.

Anti-IgLON5 disease is a rare autoimmune encephalopathy with concurrent tauopathy, characterised by sleep dysfunction and brainstem involvement. A 77-year-old woman developed obstructive sleep apnoea and recurrent hypercapnic respiratory failure requiring repeated intubation, initially misdiagnosed as epilepsy. Video recordings captured elaborate nocturnal behaviours, including praying and offering alms during sleep, alongside inspiratory stridor and sleep attacks during eating. Serial polysomnography documented progressive loss of sleep spindles and undifferentiated non-rapid eye movement sleep. Brain imaging showed only mild cortical, cerebellar and brainstem atrophy. She had anti-IgLON5 antibodies in serum and cerebrospinal fluid. Her condition partially improved after intravenous methylprednisolone and then rituximab, and she remains under follow-up. Patients with treatment-resistant sleep-disordered breathing, laryngeal dysfunction and nocturnal motor behaviours should be tested for anti-IgLON5 disease.