Helliwell PS, Porter G, Taylor WJ (2007) Polyarticular psoriatic arthritis is more like oligoarticular psoriatic arthritis, than rheumatoid arthritis. Ann Rheum Dis 66(1):113–117
McGonagle D, Conaghan PG, Emery P (1999) Psoriatic arthritis: a unified concept twenty years on [see comment][erratum appears in Arthritis Rheum 1999 Sep;42(9):1997]. Arthritis Rheum 42(6):1080–1086
Kruithof E, Baeten D, De Rycke L, Vandooren B, Foell D, Roth J et al (2005) Synovial histopathology of psoriatic arthritis, both oligo- and polyarticular, resembles spondyloarthropathy more than it does rheumatoid arthritis. Arthritis Res Ther 7(3):R569–R580
Veale DJ, Ritchlin C, FitzGerald O (2005) Immunopathology of psoriasis and psoriatic arthritis. Ann Rheum Dis 64(Suppl 2):ii26–ii29
Gladman DD, Farewell VT, Wong K, Husted J (1998) Mortality studies in psoriatic arthritis: results from a single outpatient center. II. Prognostic indicators for death. Arthritis Rheum 41(6):1103–1110
Sihvonen S, Korpela M, Laippala P, Mustonen J, Pasternack A (2004) Death rates and causes of death in patients with rheumatoid arthritis: a population-based study. Scand J Rheumatol 33(4):221–227
Gorter S, van der Heijde DM, van der Linden S, Houben H, Rethans JJ, Scherpbier AJ et al (2002) Psoriatic arthritis: performance of rheumatologists in daily practice. Ann Rheum Dis 61(3):219–224
Symmons DP, Lunt M, Watkins G, Helliwell P, Jones S, McHugh N et al (2006) Developing classification criteria for peripheral joint psoriatic arthritis Step. I. Establishing whether the rheumatologist’s opinion on the diagnosis can be used as the “gold standard”. J Rheumatol 33(3):552–557
Moll JM, Wright V (1973) Psoriatic arthritis. Semin Arthritis Rheum 3(1):55–78
Gladman DD, Shuckett R, Russell ML, Thorne JC, Schachter RK (1987) Psoriatic arthritis (PSA)—an analysis of 220 patients. Q J Med 62(238):127–141
Bennett RM (1979) Psoriatic arthritis, 9th edn. Lea & Febiger, Philadelphia
Vasey F, Espinoza LR (1987) Psoriatic arthropathy. Grune & Stratton, Orlando
Dougados M, van der Linden S, Juhlin R, Huitfeldt B, Amor B, Calin A et al (1991) The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy [see comment]. Arthritis Rheum 34(10):1218–1227
Fournie B, Crognier L, Arnaud C, Zabraniecki L, Lascaux-Lefebvre V, Marc V et al (1999) Proposed classification criteria of psoriatic arthritis. A preliminary study in 260 patients. Rev Rhum (Engl Ed) 66(10):446–456
Biondi Oriente C, Scarpa R, Pucino A, Oriente P (1989) Psoriasis and psoriatic arthritis. Dermatological and rheumatological co-operative clinical report. Acta Derm Venereol Suppl (Stockh) 146:69–71
Helliwell P, Marchesoni A, Peters M, Barker M, Wright V (1991) A re-evaluation of the osteoarticular manifestations of psoriasis. Br J Rheumatol 30(5):339–345
Jones SM, Armas JB, Cohen MG, Lovell CR, Evison G, McHugh NJ (1994) Psoriatic arthritis: outcome of disease subsets and relationship of joint disease to nail and skin disease. Br J Rheumatol 33(9):834–839
Torre Alonso JC, Rodriguez Perez A, Arribas Castrillo JM, Ballina Garcia J, Riestra Noriega JL, Lopez Larrea C (1991) Psoriatic arthritis (PA): a clinical, immunological and radiological study of 180 patients. Br J Rheumatol 30(4):245–250
Taylor W, Gladman D, Helliwell P, Marchesoni A, Mease P, Mielants H (2006) Classification criteria for psoriatic arthritis: development of new criteria from a large international study. Arthritis Rheum 54(8):2665–2673
Taylor WJ, Marchesoni A, Arreghini M, Sokoll K, Helliwell PS (2004) A comparison of the performance characteristics of classification criteria for the diagnosis of psoriatic arthritis. Semin Arthritis Rheum 34(3):575–584
Chandran V, Schentag CT, Gladman DD (2007) Sensitivity of the classification of psoriatic arthritis criteria in early psoriatic arthritis. Arthritis Rheum 57(8):1560–1563
Wright V (1959) Rheumatism and psoriasis: a re-evaluation. Am J Med 27:454–462
Veale D, FitzGerald O (1992) Psoriatic arthritis—“DIP or not DIP? That is the question”. Br J Rheumatol 31(6):430–431
Khan M, Schentag C, Gladman DD (2003) Clinical and radiological changes during psoriatic arthritis disease progression. J Rheumatol 30(5):1022–1026
Bennett AN, McGonagle D, O, Connor P, Hensor E, Coates LC, Emery P et al (2008) Early inflammatory back pain and MRI sacroiliitis: severity of osteitis at baseline and HLA B27 predict ankylosing spondylitis at 8 years. Rheumatology 47(S2):ii5 (abstract)
Williamson L, Dockerty JL, Dalbeth N, McNally E, Ostlere S, Wordsworth BP (2004) Clinical assessment of sacroiliitis and HLA-B27 are poor predictors of sacroiliitis diagnosed by magnetic resonance imaging in psoriatic arthritis. Rheumatology (Oxford) 43(1):85–88
Gladman DD, Anhorn KA, Schachter RK, Mervart H (1986) HLA antigens in psoriatic arthritis. J Rheumatol 13(3):586–592
McHugh NJ, Laurent MR, Treadwell BL, Tweed JM, Dagger J (1987) Psoriatic arthritis: clinical subgroups and histocompatibility antigens. Ann Rheum Dis 46(3):184–188
Marsal S, Armadans-Gil L, Martinez M, Gallardo D, Ribera A, Lience E (1999) Clinical, radiographic and HLA associations as markers for different patterns of psoriatic arthritis. Rheumatology (Oxford) 38(4):332–337
Kane D, Stafford L, Bresnihan B, FitzGerald O (2003) A classification study of clinical subsets in an inception cohort of early psoriatic peripheral arthritis—‘DIP or not DIP revisited’. Rheumatology (Oxford) 42(12):1469–1476
Backhaus M, Burmester GR, Sandrock D, Loreck D, Hess D, Scholz A et al (2002) Prospective two year follow up study comparing novel and conventional imaging procedures in patients with arthritic finger joints. Ann Rheum Dis 61(10):895–904
Wakefield RJ, Green MJ, Marzo-Ortega H, Conaghan PG, Gibbon WW, McGonagle D et al (2004) Should oligoarthritis be reclassified? Ultrasound reveals a high prevalence of subclinical disease. Ann Rheum Dis 63(4):382–385
Gladman DD, Farewell VT, Nadeau C (1995) Clinical indicators of progression in psoriatic arthritis: multivariate relative risk model. J Rheumatol 22(4):675–679
Clegg DO, Reda DJ, Mejias E, Cannon GW, Weisman MH, Taylor T et al (1996) Comparison of sulfasalazine and placebo in the treatment of psoriatic arthritis. A Department of Veterans Affairs Cooperative Study. Arthritis Rheum 39(12):2013–2020
Antoni C, Krueger GG, de Vlam K, Birbara C, Beutler A, Guzzo C et al (2005) Infliximab improves signs and symptoms of psoriatic arthritis: results of the IMPACT 2 trial. Ann Rheum Dis 64(8):1150–1157
Mease PJ, Goffe BS, Metz J, VanderStoep A, Finck B, Burge DJ (2000) Etanercept in the treatment of psoriatic arthritis and psoriasis: a randomised trial [see comment]. Lancet 356(9227):385–390
Korendowych E, Dixey J, Cox B, Jones S, McHugh N (2003) The influence of the HLA-DRB1 rheumatoid arthritis shared epitope on the clinical characteristics and radiological outcome of psoriatic arthritis. J Rheumatol 30(1):96–101
Ho PY, Barton A, Worthington J, Plant D, Griffiths CE, Young HS et al (2007) Investigating the role of the HLA-Cw*06 and HLA-DRB1 genes in susceptibility to psoriatic arthritis: comparison with psoriasis and undifferentiated inflammatory arthritis. Ann Rheum Dis 67:677–682
Korendowych E, Owen P, Ravindran J, Carmichael C, McHugh N (2005) The clinical and genetic associations of anti-cyclic citrullinated peptide antibodies in psoriatic arthritis. Rheumatology (Oxford) 44(8):1056–1060
Taylor WJ, Zmierczak HG, Helliwell PS (2005) Problems with the definition of axial and peripheral disease patterns in psoriatic arthritis. J Rheumatol 32(6):974–977