HLA is a candidate region for psoriatic arthritis. evidence for excessive HLA sharing in sibling pairs.

Psoriatic arthritis (PsA) is an inflammatory arthritis that may affect as many as 30% of patients with psoriasis (Ps). Genetic factors play an important role in the susceptibility to and the expression of PsA. The objective of this study was to identify whether haplotype sharing among affected sibling pairs of individuals with PsA is increased compared with unaffected sibling pairs. We collected 182 sibling pairs of probands affected with PsA. Extracted genomic DNA was amplified in polymerase chain reactions using locus specific primers homologous to nucleotide sequences for each of the HLA-A, -B, -C, -DR, and -DQ loci. Polymerase chain reaction amplicons were identified by reverse line blot assay using sequence-specific oligonucleotide probes. Evidence for excessive haplotype sharing was examined through Green and Woodrow's test. Results indicate that of the 182 sibling pairs, 46 were affected by PsA, 48 by Ps, and 88 were unaffected. The sharing of 2, 1, and 0 haplotypes for the PsA affected sibling pairs was 14, 27, and 5, respectively (p = 0.04); whereas the haplotype sharing for the Ps affected sibling pairs was 12, 26, and 10, respectively (p = 0.38). In conclusion, the human leukocyte antigen region on chromosome 6p is implicated as one of the candidate regions in PsA.

Prevalence of malignancy in psoriatic arthritis.

OBJECTIVE: To determine the prevalence and types of malignancy in a large cohort of patients with psoriatic arthritis (PsA), and to compare this rate with that in the general population. METHODS: A cohort analysis of patients who were followed up prospectively from 1978 to 2004 at the University of Toronto Psoriatic Arthritis Clinic was performed. Patients were followed up at 6-12-month intervals according to a standard protocol, which included recording of malignancy, and tracked on a computer database. The cohort was linked with a provincial database to find malignancies that may have been missed by the protocol or developed after patients were lost to followup. Data were presented and analyzed using descriptive statistics and the Cox regression model with robust estimate of variance. Rates of first malignancy in the cohort were compared with rates in the population to derive standardized incidence ratios (SIRs). RESULTS: Of the 665 patients included, 68 (10.2%) developed a malignancy at an average age of 62.4 years. The most frequently seen malignancies were breast (20.6%), lung (13.2%), and prostate (8.8%) cancer. The SIR for all cancers was 0.98 (95% confidence interval 0.77-1.24). Overall cancer type-specific SIRs were 0.69 (95% CI 0.26-1.83) for hematologic and 0.88 (95% CI 0.46-1.69) for lung cancer. In females, the SIR for breast cancer was 1.55 (95% CI 0.92-2.62), and in males, the SIR for prostate cancer was 0.65 (95% CI 0.29-1.44). CONCLUSION: Overall, 10.2% of patients in the Toronto PsA cohort developed cancer. The most frequent cancers were breast, lung, and prostate cancer. The incidence of malignancy in the large PsA cohort did not differ from that in the general population.

The clinical assessment of patients with psoriatic arthritis: results of a reliability study of the spondyloarthritis research consortium of Canada.

OBJECTIVES: To evaluate whether rheumatologists experienced in psoriatic arthritis (PsA) assess peripheral and axial involvement in the same way and to consider core clinical measurements that should be included in clinical trials in PsA. METHODS: Ten patients with PsA, representing a broad range of joint inflammation, joint damage, and spinal involvement, were selected for the study. Each patient was examined by each of 10 rheumatologists, members of the Spondyloarthritis Research Consortium of Canada, according to a Latin Square design. Assessments included scoring actively inflamed joints and damaged joints, dactylitis, enthesitis, and spinal measurements. Variance components analyses were conducted for continuous measurements based on models with observer, patient, and order effects. Estimates of intraclass correlation coefficients and associated 95% confidence intervals were obtained. RESULTS: There was substantial reliability in the assessment of the number of actively inflamed joints and excellent agreement in the number of damaged joints. Only moderate agreement was found for the number of digits with dactylitis. There was excellent agreement among observers in the intermalleolar distance measurements, but there was not as good agreement in the other measurements of spinal mobility. There was good agreement among the observers in detecting plantar fasciitis, however, the other entheses did not fare as well. CONCLUSION: In this first multicenter study of the assessment of clinical evaluation of patients with PsA we found that the assessment of peripheral joint disease is reliable although training should be performed prior to initiation of drug trials or comparative studies in this disease. The assessment of back measurements in PsA and other spondyloarthritis requires further study.