Prevalence of Peripheral and Extra-articular Manifestations
Recently, a number of national SpA registries have described the clinical characteristics of the included patients. The results of the German Spondyloarthritis Inception Cohort were published by Rudwaleit et al. They described the early disease stage in axial SpA by comparing in a cross-sectional analysis 226 patients with nonradiographic axial SpA (nr-axSpA; symptom duration ≤ 5 years) and 236 patients with AS (symptom duration ≤ 10 years). The two groups did not differ in the frequency of HLA B27 positivity and inflammatory back pain, but also with regard to peripheral manifestations such as arthritis, enthesitis and dactylitis, there was no significant difference. Current peripheral arthritis was observed in 14.4% of AS patients compared to 18.2% in nr-axSpA; likewise, enthesitis was detected in 20.8 and 24.8%, and dactylitis in 2.1 and 3.1%, respectively. Looking at the percentage of patients that had ever experienced arthritis or enthesitis, the numbers rose to approximately 40% in both groups. In the Spanish Registro de Espondiloartritis de la sociedad espanola de reumatologia-cohort, a total of 150 SpA patients were selected because of a disease course of 2 years or less from the onset of symptoms; the majority of these patients suffered from AS (n = 46), PsA (n = 51) or undifferentiated SpA (USpA) (n = 43). On inclusion, peripheral arthritis was observed in 20% of AS, 51% of PsA and 21% of USpA patients, whereas enthesitis was observed in 24, 14 and 26%, respectively. An interesting cohort is the French Devenir des Spondyloarthropathies Indifferenciées Récentes cohort. In this nation-wide, prospective follow-up study, patients presenting with early inflammatory back pain are followed in order to set up a database to facilitate investigations on diagnosis, prognosis and epidemiology in the field of SpA. Dougados et al. published the baseline results of the 708 recruited patients. Peripheral arthralgia (past history or current symptoms) was observed in 56.9% of all patients; synovitis was observed in 21.3%. Comparable percentages were observed regardless of the classification criteria used. Likewise enthesiopathy was observed in 49% of patients (any site) and in 41.5% of patients at the heel. Extra-articular manifestations were also reported; acute anterior uveitis occurred in 8.5% of patients, inflammatory bowel disease in 4.2% and psoriasis in 15.8%.
Finally, a large series of Brazilian patients with SpA was published by de Carvalho et al. The authors describe 1505 patients fulfilling the ESSG classification criteria. Clinical and demographic variables were recorded; AS was the most frequent disease (65.4%), followed by PsA (18.4%) and USpA (6.7%). The influence of sex on the disease pattern was studied; the 415 female patients were significantly older and reported shorter disease duration compared with male patients; the female sex was associated to peripheral arthritis and dactylitis, a higher number of painful and swollen joints and a higher MASES score (Maastricht Ankylosing Spondylitis Enthesitis Score), whereas pure axial involvement was more frequently observed in men. A similar increased frequency of peripheral arthritis in female AS patients was found in the Icelandic population. In our own prospective cohort of consecutive, newly diagnosed SpA patients (unpublished data), we have included over the past year 85 patients with predominantly axial SpA (41 AS, 44 nr-axSpA). The data on peripheral manifestations are consistent with the international cohorts presented above. The percentage of peripheral arthritis is 17.1% in AS and 25.6% in nr-axSpA; percentages for enthesitis are 22 and 25%, respectively.
The importance of peripheral arthritis cannot be underestimated. In one retrospective analysis of 271 AS patients (according to modified New York criteria), 84 had peripheral arthritis. In these patients a significantly higher prevalence of childhood onset (36 vs. 25%, P = 0.04), hip joint involvement (55 vs. 44%, P = 0.04), dactylitis (10 vs. 1%, P = 0.0006), enthesitis (28 vs. 7%, P = 0.0006) and uveitis (36 vs. 20%, P = 0.005) was observed.