Idiopathic
uveitis is the most common form of chronic
uveitis seen in our area. Characteristically it is a heterogeneous entity in its clinical severity, evolution and therapeutic response, and immune mechanisms are thought to be involved. The phenotype frequencies of
HLA antigens were studied in 62 patients with idiopathic
uveitis and compared with their frequencies in northern Portugal. The authors also included two groups with a well known immunogenetic background-Behçet's syndrome (BS: n=20) and
ankylosing spondylitis (AS: n=18) which are, respectively, the most severe and the most frequent of the rheumatic forms in the area. An increased frequency of
HLA B5(B51) in Behçet
uveitis (55%; RR=8) was confirmed in the authors' population. They also found in idiopathic
uveitis an increased risk for HLA B27 (RR=14). HLA B27 positive idiopathic
uveitis was predominantly unilateral (80%) and anterior (97%), whereas B27 negative forms showed a higher prevalence of severe
panuveitis. In conclusion, the authors confirmed in their population the association of HLA B27 with
uveitis, and HLA B51 with Behçet
uveitis. In this last entity an intermediate frequency between northern Europe and the Mediterranean area was observed.