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 (<or=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.