OBJECTIVE: To determine the clinical features of psoriatic arthritis (PsA) in a multiethnic Oriental population and to study the effect of ethnicity on disease patterns.
METHODS: A retrospective study of 80 patients with PsA seen at either a rheumatology or dermatology referral center. Patients and case records were reviewed and data abstracted according to a standard protocol. Eighty consecutive patients with psoriasis without PsA seen at the dermatology center were recruited as controls.
RESULTS: Asymmetric polyarthritis developing in the 4th decade with an equal male to female ratio was the commonest pattern of arthritis among Chinese, Indians, and Malays. Clinically apparent lumbar spondylitis was significantly more common in Indians than Chinese (10/11 vs 11/20, respectively; p = 0.046), although the prevalence of lumbar spondylitis was similar in all ethnic groups. Eighty-nine percent of subjects required nonsteroidal antiinflammatory drugs and 51% required disease modifying antirheumatic drugs at some time for control of joint disease. PsA was significantly more common among Indians compared to the ethnic distribution of the Singapore population (p < 0.000001). Multiple logistic regression identified Indian ethnicity as a risk factor for the development of PsA (OR 2.39, 95% confidence interval 1.02 to 5.60).
CONCLUSION: The commonest pattern of PsA in all ethnic groups was asymmetric polyarthritis. Ethnicity affected the development and presentation of PsA in our series: Indians with psoriasis had double the risk of developing PsA compared to Chinese with psoriasis, and lumbar spondylitis when present in Chinese subjects was asymptomatic in 45%, being detectable only on radiological examination.
Geographic differences in manifestation of psoriatic arthritis (PsA) could be related to differences in genetic or environmental factors. We aimed to compare the disease activity and functional status using validated outcome measures among patients with PsA of different ethnicities living in the same environment. We performed a cross-sectional study on consecutive patients with PsA classified by the Classification Criteria for Psoriatic Arthritis (CASPAR) criteria from a single center. Sociodemographic data, clinical variables, and patient-reported outcomes were collected using a standardized protocol. Disease activities were assessed by validated composite scores: clinical Disease Activity Index for Psoriatic Arthritis (cDAPSA), Composite Psoriatic Disease Activity Index (CPDAI), and minimal disease activity (MDA). Physical function was assessed with Health Assessment Questionnaire (HAQ) and the Medical Outcome Study Short-Form 36 (SF36) physical function subscales. Linear regression analyses were performed to identify variables associated with disease activities and physical function. Ninety-eight patients (51.5%, men) with mean (±SD) age and duration of PsA of 51.5 ± 13.8 and 5.5 ± 8.4 years were recruited. Indian was overrepresented compared with the national distribution of ethnicities. Compared to Chinese, Indian patients were more likely to be using biological therapies, have higher tender joint count, and worse enthesitis. Higher proportion of Indians had higher disease activity categories measured by cDAPSA, CPDAI, and MDA and had poorer physical function. In the multivariable analysis, ethnicity was significantly associated with HAQ and SF36-PF. Compared to Chinese, Indians with PsA living in the same environment had worse disease activity and physical function measured by validated outcomes.
Study site: Psoriatic arthritis clinic in a tertiary referral center, Singapore