HLA-DQB1 Allele and Hypocretin in Korean Narcoleptics with Cataplexy

Abstract

Cataplexy is one of the most pathognomonic symptoms in narcolepsy. This study was designed to investigate the frequency of the HLA-DQB1 allele and cerebrospinal fluid (CSF) hypocretin levels in Korean narcoleptics with cataplexy as compared with those who do not have cataplexy. Seventy-two narcoleptics were selected based on polysomnography and multiple sleep latency test as well as their history and clinical symptoms at Sleep Disorders Clinic. The patients were divided into a narcolepsy with cataplexy group (n=56) and a narcolepsy without cataplexy group (n=16). All patients were subjected to HLA typing to determine the frequency of DQB1 allele and to spinal tapping to measure the level of CSF hypocretin. In cataplexy-positive patients, as compared with cataplexy-negative patients, the frequency of HLA-DQB1*0602 was found to be significantly high (89.3% vs. 50.0%) (p=0.003). On the other hand, the frequency of HLA-DQB1*0601 was found to be significantly low (0% vs. 43.8%) (p<0.001). In 48 of 56 cataplexy-positive patients (85.7%), hypocretin levels were decreased (≤110 pg/mL). However, only 6 of 16 cataplexy-negative patients (37.5%) exhibited a decreased hyopcretin level (p<0.001). The high frequency of HLA-DQB1*0602, low frequency of HLA-DQB1*0601 and low hypocretin levels in cataplexy-positive groups suggest that cataplexy-positive narcolepsy might be an etiologically different disease entity from the cataplexy-negative.