Anti-IgLON5 disease with severe central sleep apnea-hypopnea syndrome: A case report.

Anti-IgLON family protein 5 (IgLON5) antibody-related encephalitis is a rare but increasingly recognized central nervous system autoimmune disease. It displays heterogeneity in clinical presentation. As the clinical case repository expands, our understanding of the disease's clinical phenotypes and therapeutic approaches continues to evolve. This report details a 73-year-old male's case, initially misdiagnosed with narcolepsy due to excessive daytime sleepiness and sleep-related involuntary behaviors, but later found to have severe respiratory disturbances, diverging from narcolepsy. During treatment, the patient's condition progressed to respiratory failure, necessitating further investigation. Diagnosis was confirmed through positive serum and cerebrospinal fluid (CSF) tests for anti-IgLON5 antibodies. Treatment with continuous positive airway pressure (CPAP), immunoglobulin pH4, and corticosteroids significantly improved his condition. This case underscores the critical need for awareness of anti-IgLON5 encephalitis within the differential diagnosis of complex sleep disorders, highlighting its potential for severe progression and the challenges associated with its diagnosis.