Prevalence, clinical features and treatment pattern of patients with concurrent diagnoses of rheumatoid arthritis and psoriatic disease: results of a 14-year retrospective study in a tertiary referral center

Background: Multiple comorbidities, including rheumatoid arthritis (RA), have been reported to be associated with psoriasis. Objective: This study aimed to determine the prevalence and the clinical features of RA among patients with psoriasis in a tertiary referral center. Methods: Between January 2000 and December 2013, all patients coded with psoriatic disease (ICD-9 CM 696.0 OR ICD-9 CM696.1) and RA (ICD-9 CM 714.0) in a tertiary medical center were enrolled. Results: There were 10,844 patients and 9073 patients with psoriatic disease and RA identified by diagnostic codes, respectively. Among patients with psoriasis, 111 patients had claim-based diagnosis of RA (1.02%). By reviewing medical records and telephone interview or clinic visits, 25 of the 111 patients (0.23%) was identified unequivocally as having concurrent RA. Among them, 17 (68%) were female and 16 (64%) patients developed arthritis prior to the onset of psoriasis with a mean lag of 6.3 years (1-19 years); 8 (32%) had psoriasis skin lesions prior to the onset of arthritis with a mean lag of 6.9 years (3-20 years); 1 (4%) had skin lesions and arthritis in the same time; 17 (68%) patients also fulfilled the CASPAR classification criteria for psoriatic arthritis. The mean age of onset for arthritis was 49.6 years old. Conclusions: The prevalence of RA in psoriasis might be overestimated in some previous studies using claimed database. Patients with concurrent RA and psoriasis showed a comparable age of onset and male to female ratio, but had more axial involvements compared to patients without psoriasis.