title: Association of narcolepsy-cataplexy with HLA-DRB1 and DQB1 in Mexican patients: a relationship between HLA and gender is suggested.
abstract: BACKGROUND
  Narcolepsy-cataplexy is characterized by excessive daytime sleepiness with recurrent episodes of irresistible sleep, cataplexy, hallucinations and sleep paralysis. Its aetiology is unknown, but it is positively associated with the human leukocyte antigens (HLA) in all studied populations. The purpose of the present study was to investigate the association of HLA class II DRB1/DQB1 alleles with narcolepsy-cataplexy in Mexican Mestizo patients.
  
  
  METHODS
  This is a case-control study of consecutive patients and ethnically matched controls. We included 32 patients diagnosed with typical narcolepsy-cataplexy, of the National Institute of Neurology, of the Institute of Psychiatry and at the Center of Narcolepsy at Stanford University. As healthy controls, 203 Mexican Mestizos were included. DRB1 alleles were identified using sequence based typing. A PCR-SSOP reverse dot blot was used for DQB1 typing. Allele frequency was calculated by direct counting and the significance of the differences was assessed using the Yates Chi square. Odds ratio and confidence intervals were evaluated.
  
  
  RESULTS
  HLA-DRB1*1501 (OR = 8.2; pc < 0.0001) and DQB1*0602 (OR = 8.4; pc < 0.0001) were found positively associated with narcolepsy. When deleting DQB1*0602+ patients from the analysis, DQB1*0301 was also found increased (OR = 2.7; p = 0.035; pc = NS). DQB1*0602/DQB1*0301 genotype was present in 15.6% of the cases (OR = 11.5; p = 0.00035), conferring a high risk. DRB1*0407 (OR = 0.2; p = 0.016 pc = NS) and DQB1*0302(OR = 0.4; p = 0.017, pc = NS) were found decreased in the patients. The gender stratification analysis showed a higher risk in females carrying DRB1*1501 (OR = 15.8, pc < 0.0001) and DQB1*0602 (OR = 19.8, pc < 0.0001) than in males (OR = 5.0 for both alleles; p = 0.012, pc = NS for DRB1 & p = 0.0012, pc = 0.017 for DQB1). The susceptibility alleles found in Mexicans with narcolepsy are also present in Japanese and Caucasians; DRB1*04 linked protection has also been shown in Koreans. A stronger HLA association is suggested in females, in accordance with the sexual dimorphism claimed previously.
  
  
  CONCLUSIONS
  This knowledge may contribute to a better understanding of the disease pathogenesis in different populations. The evaluation of the risk to develop narcolepsy-cataplexy in carriers of the described alleles/genotypes may also be possible. A larger sample should be analysed in Mexican and in other Hispanic patients to confirm these results.
authors.affiliation: Department of Immunology and Immunogenetics, InDRE, Mexico City, Mexico. calaez@hotmail.com
authors.forename: Carmen
authors.initials: C
authors.lastname: Alaez
authors.forename: Ling
authors.initials: L
authors.lastname: Lin
authors.forename: Hilario
authors.initials: H
authors.lastname: Flores-A
authors.forename: Miriam
authors.initials: M
authors.lastname: Vazquez
authors.forename: Andrea
authors.initials: A
authors.lastname: Munguia
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mignot
authors.forename: Reyes
authors.initials: R
authors.lastname: Haro
authors.forename: Harry
authors.initials: H
authors.lastname: Baker
authors.forename: Clara
authors.initials: C
authors.lastname: Gorodezky
mesh_terms: D000483:Alleles; D016022:Case-Control Studies; D002385:Cataplexy / Q000235:genetics*; D016009:Chi-Square Distribution; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006683:HLA-DQ Antigens / Q000235:genetics*; D059866:HLA-DQ beta-Chains; D006684:HLA-DR Antigens / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006650:Histocompatibility Testing; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D008800:Mexico; D009290:Narcolepsy / Q000235:genetics*; D012737:Sex Factors
chemical_list: D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; D008562:Membrane Glycoproteins