Human Leukocyte Antigen-Typing in Patients with Excessive Daytime Sleepiness

Narcolepsy is a disorder recognized by excessive daytime sleepiness (EDS). Several studies demonstrated its association with human leukocyte antigen (HLA) DQB1*0602, DQA1*0102, and DRB1*15. Our study aimed to perform HLA-typing on patients with EDS. Moreover, we performed HLA-typing for family members of the patients.
We studied 83 patients with EDS and 77 of their first-degree relatives. Patients filled out a questionnaire including Epworth Sleepiness Scale (ESS), and underwent polysomnography (PSG) and multiple sleep latency test (MSLT). The whole blood samples were drawn from the patients and their families for HLA typing (class II). International classification of sleep disorders-2 (ICSD-2) criteria was used as the gold standard for diagnosing narcolepsy.
HLA DQB1*0602 was present in 20 (45.5%) of narcoleptic patients and 2 (5.1%) of patients with other causes of EDS. Prevalence of DQB1*0602 in family members of narcoleptic patients were higher than family members of patients with other causes of EDS (38% vs. 11.1%, P = 0.06). DQB1*0602, DQA1*0102, and DRB1*15 were more prevalent in narcoleptic patients with cataplexy than narcoleptic patients without cataplexy and patients with other causes of EDS. The sensitivities of the DQB1*0602 for diagnosing narcolepsy, narcolepsy with cataplexy, and narcolepsy without cataplexy were 40%, 60%, and 20%, respectively; while specificities were 93.9%, 87.9%, and 70.6%, respectively.
HLA typing can be helpful in patients with atypical cataplexy and inconclusive MSLT results. More studies of Iranian narcoleptic patients are required for analyzing their HLA sequences.