Anti-streptococcal antibodies in Chinese patients with type −1 narcolepsy

Background Narcolepsy type 1 (NT1) is considered to be an autoimmune disease, and streptococcal infection may be an environmental trigger. However, previous studies from Asian narcolepsy patients did not reveal elevated anti-streptolysin O [ASO]. The aim is to investigate whether large sample Chinese patients with NT1 have an increase in antistreptococcal antibody titers. Methods A total of 214 narcolepsy patients and 360 healthy controls were recruited. All patients were DQB1∗0602 positive with clear-cut cataplexy or had low CSF hypocretin-1. Participants were tested for ASO and anti DNAse B [ADB]. These patients were divided into five groups according to disease duration, including 29 patients less than 3 months; 25 from 3 months to 1 year; 40 from 1 to 3 years; 61 from 3 to 10 years and 59 patients over 10 years. Comparison was also made between children and adults with age matched controls, respectively. Results There were no significant differences between patients and healthy controls in regard to both ASO ≥200 IU (19.2% vs. 16.9%, p = 0.50) and ADB≥480IU (9.8% vs. 10.3%, p = 0.86). For children narcolepsy patients, ASO positive rates (19.8% vs. 18%, p = 0.68) and ADB positive rates (10.4% vs. 12%, p = 0.72) had no differences compared to age matched controls. No difference was observed in adult narcolepsy patients either, with ASO positive rates (18.5% vs. 13.8%, p = 0.39) and ADB positive rates (9.3% vs. 5.3%, p = 0.42) compared to age matched controls, respectively. ASO and ADB positive rates had no significant differences among different disease duration groups (p = 0.55 and 0.9, respectively). Conclusion Streptococcus infection reflected by increase of ASO and ADB levels was not found in Chinese patients with type 1 narcolepsy, additional triggers for narcolepsy need to be addressed in this population.