Pediatric Rheumatology Online Journal → June 2003 → Enthesitis-related arthritis and Psoriatic arthritis→ Abstract #23

LINKAGE ANALYSIS IN JUVENILE ONSET SPONDYLOARTHROPATHIES (SpA). A STUDY OF MEXICAN FAMILIES WITH MULTIPLE CASES

R. Gutierrez-Suarez,¹ R. Burgos-Vargas.¹

¹Research Division, Hospital General de Mexico, Mexico, DF, Mexico

INTRODUCTION:  Case-control studies and particularly linkage studies of families with multiple cases have demonstrated that HLA-B27 determines the individual<rsquo>s susceptibility to ankylosing spondylitis (AS), but recurrence risk modelling shows genetic susceptibility is oligogenic. In this context, various major histocompatibility complex (MHC) and non-MHC genes have been implicated in disease susceptibility.
OBJECTIVE:  To determine the role of MHC genes in SpA susceptibility by linkage analysis in multiplex-case families of Mexican descent, in which at east one case has juvenile onset disease.
Methods: 121 individuals from 16 families included in the study underwent clinical and HLA tissue typing by PCR/SSO. Classification and diagnosis were based on the ESSG (SpA) and New York modified (AS) criteria. Radiographic studies were carried out in symptomatic cases. Juvenile and adult onset disease haplotypes were compared and haplotype sharing identical by descent (IBD) analysed.
RESULTS: Thirty-eight individuals had SpA or AS. Twenty-five (65.7%) sib pairs shared two haplotypes, nine (23.6%) one, and four (10.5%) none. This was significantly different from random expectations (x=33.7, p10^-6). All shared haplotypes, but 4 included HLA-B27. The distribution of all other alleles was heterogeneous, yet HLA-DR4 and DR8 prevailed in several families. There were no differences between juvenile and adult onset disease haplotypes.
CONCLUSION:  This study confirming linkage of HLA and AS, as well the lack of any significant differences between juvenile and adult familial cases. There are at least two-thirds of sib-pairs sharing HLA-B27 and one additional haplotype.