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Anterior uveitis (AU) is the most common form of uveitis,1-3 and may be produced by different causes. An aetiological diagnosis is commonly established in approximately half of the patients with AU, being seronegative spondyloarthropathies (SA), and mainly ankylosing spondylitis, the most frequent cause of the disease. Approximately 50% of the patients with AU are HLA-B27 positive; half of them usually presenting with associated SA,4-8 the other half are patients with HLA-B27+ but with no associated articular disease (HLA-B27+ AU). Several clinical features have been described to be common in patients with AU associated with HLA-B27, however, these features are similar either in patients with or without associated SA.9 10 This is why we conducted this clinical and immunological study in patients with AU positive for HLA-B27 with the aim of discovering the differences between patients with and without associated SA.
A prospective study was conducted involving 146 patients with active AU seen between April 1988 and October 1995 referred from an ophthalmologist with the syndromic diagnosis of AU of unknown origin. Patients were classified in three aetiological groups: (1) Idiopathic anterior uveitis (IAU), all were HLA-B27−, (2) HLA-B27+ AU without associated SA, and (3) HLA-B27+ AU with associated SA.
Of the 146 patients with AU studied, 98 had IAU (67.1%) and 48 were positive for HLA-B27; of them, 19 (13%) had associated SA (HLA-B27+ AU with SA), and 29 (19.9%) did not (HLA-B27+ AU). No significant differences were found in clinical features of AU between the three study groups. Erythrocyte sedimentation rate, C reactive protein and IgA were found to be more increased in patients than in control, although without differences between the three groups of patients. With regard to lymphocyte populations, we found some differences between our AU patients and control group (table 1). Patients with IAU showed lower percentages (mean (SEM)) of CD4CD45R+ (15.47 (9.49)%) than controls (25.20 (7.76)%) and patients with SA (21.97 (10.16)%) (fig 1). Patients with IAU had higher percentages of CD4CD45R- (28.46 (7.89)%) than SA patients (23.23 (6.81)%) and the control group (20.77 (6.40)%) (fig 2).
Associated systemic pathology was demonstrated in 13% of the cases (19 patients with seronegative SA), 29 patients (19.9%) were HLA-B27+ without SA; not associated disease was found in the other 98 cases of AU (67.1%), which were classified as idiopathic. Seronegative SA are the most frequent entities found in uveitis patients, representing between 6%2 and 13%3 of all forms of uveitis, and 20 to 25% of the AU. HLA-B27+ AU without associated SA represents about 25% of the AUs; it has been considered by some authors a “frustrated” or monosymptomatic form of ankylosing spondylitis,11 but today, it is still unclear as to whether or not it is the same clinical entity, or whether these patients will develop seronegative SA in future. We did not find differences in clinical features of AU between HLA-B27+ and HLA-B27− patients. A deficit of CD4CD45R+ (suppressor-inducer T lymphocytes) and an increase of CD4CD45R− (memory T lymphocytes), such as in our patients with IAU, have been described in certain autoimmune disease, suggesting that these disorders could be attributable to these changes.12-15 In addition, differences found in the values of CD4CD45R cells between patiens with IAU and SA suggest a different physiopathogenetic mechanism in the development of both diseases. The immunological features studied, both humoral and cellular, in HLA-B27+ patients without associated SA were similar to those of patients with SA, which suggest a common pathogenetic link between both forms of AU. It is possible that the long term follow up of these patients will clarify whether or not it is the same entity.
We are indebted to Ms E Velasco for assistance in the preparation of the manuscript.
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