Traditional biomarkers in narcolepsy: experience of a Brazilian sleep centre / Biomarcadores tradicionias em narcolepsia: experiência de um centro de sono brasileiro

This study was thought to characterized clinical and laboratory findings of a narcoleptic patients in an out patients unit at São Paulo, Brazil. METHOD: 28 patients underwent polysomnographic recordings (PSG) and Multiple Sleep Latency Test (MSLT) were analyzed according to standard criteria. The analysis of HLADQB1*0602 allele was performed by PCR. The Hypocretin-1 in cerebral spinal fluid (CSF) was measured using radioimmunoassay. Patients were divided in two groups according Hypocretin-1 level: Normal (N) - Hypocretin-1 higher than 110pg/ml and Lower (L) Hypocretin-1 lower than 110 pg/ml. RESULTS: Only 4 patients of the N group had cataplexy when compared with 14 members of the L group (p=0.0002). DISCUSSION: This results were comparable with other authors, confirming the utility of using specific biomarkers (HLA-DQB1*0602 allele and Hypocretin-1 CSF level) in narcolepsy with cataplexy. However, the HLADQB1*0602 allele and Hypocretin-1 level are insufficient to diagnose of narcolepsy without cataplexy.

Este estudo foi idealizado para avaliar as características clinicas e laboratoriais de uma população de narcolépticos atendidos num centro de referência na cidade de São Paulo (Brasil). MÉTODO: 28 pacientes realizaram polissonografia e teste de múltiplas latências do sono segundo critérios internacionais. O alelo HLADQB1*0602 foi identificado por PCR. A Hipocretina-1 no líquido cefalorradiano (LCR) foi mensurada por radioimunoensaio. Os pacientes foram divididos em 2 grupos conforme o nível de Hipocretina-1. Normal (N) - Hypocretin-1 >110pg/ml e baixa (B) - Hypocretina-1 <110pg/ml. RESULTADOS: Somente 4 pacientes do grupo N tinham cataplexia quando comparados com 14 pacientes do grupo B (p=0,0002). DISCUSSÃO: Estes resultados foram comparáveis com outros autores, confirmando a utilidade do uso de biomarcadores específicos (HLA-DQB1*0602 e nível da hipocretina-1 no LCR) em narcolepsia com cataplexia. Porém, o alelo HLADQB1*0602 e a dosagem da Hipocretina-1 são insuficientes para o diagnóstico da narcolepsia sem cataplexia.

Sistema hipocretinérgico y narcolepsia / Hypocretin system and narcolepsy

Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep-onset rapid eye movement (REM) sleep periods. It is now identified as a neurodegenerative disease because there is a massive loss of specific neurons in the brain. These neurons contain the neuropeptides hypocretin-1 and hypocretin-2, which are also known as orexin-A and orexin-B. Cerebrospinal fluid hypocretin-1 measurements are diagnostic for primary narcolepsy. The cause of neural loss could be autoinmune since most patients have the HLA DQB1*0602 alíele that predisposes to the disorders. The discovery of hypocretin deficiency is redefining the clinical entity of narcolepsy and offering novel diagnostic procedures. This article reviews the current understanding of narcolepsy and discusses the implications of hypocretin discovery (Rev Méd Chile 2009; 137:1209-16).

HLA-DQB1 Allele and Hypocretin in Korean Narcoleptics with Cataplexy

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.