Clinical, radiographic and HLA associations as markers for different patterns of psoriatic arthritis

Objective. The aim of this study was to examine whether the five clinical f orms of psoriatic arthritis (PsA) identified by Moll and Wright (Semin Arth ritis Rheum 1973;3:55-78) could be clearly distinguished, especially as the disease evolved over time, to analyse whether radiographic features or HLA associations could define subsets with greater precision and to identify p redictors of disease outcome. Methods. Seventy-three patients (37 males and 36 females) were followed for a median time of 8 yr (range 1-16 yr). A standard clinical protocol was us ed to assess patients at each visit and two clinical scores, based on the j oint areas involved, were defined to evaluate the mode of onset and the evo lution of arthritis. X-ray films of the hands, feel and sacroiliac joints w ere taken and the patients were divided into two categories according to th e presence or absence of erosions and an X-ray erosion score was also used. Three classification methods were used to define the different clinical su bsets. HLA-A. B and DR antigens were tested by standard microlymphocytotoxi city assays. A multiple linear regression model was used in the statistical analysis. Results. The five classical clinical subsets defined by Moll and Wright did not remain since distinct peripheral arthritis patterns tended to evolve o ver lime. Only two discrete groups were identified, axial disease (AD) (sac roilitis with or without peripheral arthritis) in 29% of cases and peripher al disease (PD) without sacroilitis in 71%. AD was positively associated wi th the duration of arthritis (P < 0.01). presence of mutilation (P < 0.02) and the joint area score over disease evolution (JASE) (P < 0.02). There we re erosions in 71% of the patients. Erosions correlated with the presence o f mutilation (P < 0.007) and with the JASE (P < 0.0005). HLA-B27 was found in 43% of patients with ADI but only in 11% of PD patients (P < 0.01). No o ther clear HLA correlations were found. Conclusions. Despite the relatively small number of patients, this longitud inal study suggests that only two clinical subsets can be clearly defined i n PsA, AD and PD; these are primarily determined on clinical grounds althou gh HLA-B27 is strongly associated with AD. The evolution of PD pattern with time means that narrower peripheral arthritis subsets are of little clinic al use.