546 CLINICAL REPORT
ActaDV ActaDV Advances in dermatology and venereology Acta Dermato-Venereologica
Duration of Psoriatic Skin Disease as Risk Factor for Subsequent Onset of Psoriatic Arthritis
Alexander EGEBERG 1, Lone SKOV 1, Claus ZACHARIAE 1, Gunnar H. GISLASON 2 – 4, Jacob P. THYSSEN 1 and Lotus MALLBRIS 5
1
Department of Dermatology and Allergy and 2 Department of Cardiology, Herlev and Gentofte Hospital, University of Copenhagen, Hellerup,
3
The Danish Heart Foundation, 4 The National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark, and 5 Eli Lilly and Company, Indianapolis, IN, USA
It is unclear whether psoriasis is a progressive disease that requires early aggressive intervention. This population-based study identified patients with psoriasis and psoriatic arthritis( PsA). Survival analysis and Kaplan – Meier life table techniques were used. The study comprised 10,011 psoriasis patients( severe n = 4,618), and 1,269 patients also had PsA. Incidence of PsA increased with duration of cutaneous symptoms( p = 0.0001). Psoriasis diagnosed before age 20 or 30 years, respectively, suggested a lower risk of PsA than psoriasis diagnosed after age 50 years, yet age at first cutaneous symptoms did not predict development of PsA. No clear association with disease severity was found. PsA incidence appeared stable with longer duration of psoriasis, but further data are needed to firmly establish the relationship with age of psoriasis onset.
Key words: psoriasis; psoriatic arthritis; disease duration; epidemiology.
Accepted Feb 20, 2018; Epub ahead of print Feb 28, 2018 Acta Derm Venereol 2018; 98: 546 – 550.
Corr: Alexander Egeberg, Department of Dermatology and Allergy, Herlev and Gentofte Hospital, Kildegårdsvej 28, DK-2900 Hellerup, Denmark. E- mail: alexander. egeberg @ gmail. com
Cutaneous psoriasis( henceforth“ psoriasis”) is a manifestation of psoriatic disease, a chronic systemic inflammatory condition that affects 2 – 3 % of Europeans, and up to 8 % of populations in isolated parts of the northern Europe, in particular Scandinavia( Norway)( 1). Plaque psoriasis( psoriasis vulgaris) is the most common form of psoriasis and is reported to account for almost 90 % of all cases( 2). The majority of patients( approximately 70 – 80 %) have mild disease, i. e. psoriasis that can be managed with topical treatment alone( 2, 3). Clinically, psoriasis is characterized by sharply demarcated hyperkeratotic and scaling plaques, which may be either localized or widespread, and a common extracutaneous manifestation includes psoriatic arthritis( PsA)( 4).
Psoriasis and PsA frequently co-exist( 5, 6). Patients with PsA display increased inflammation of the peripheral joints and skeleton, and may also have extra-articular manifestations, such as enthesitis and other musculoskeletal manifestations( 7, 8). While severity and prevalence of the different disease manifestations in PsA can differ greatly, the clinical picture may sometimes overlap with that of seronegative rheumatoid arthritis and ankylosing spondylitis, making the diagnosis difficult( 8). It is wellestablished that most patients with PsA develop psoriasis prior to onset of their arthritic symptoms, but the exact clinical relationship is insufficiently understood( 9). For example, some studies have suggested a relationship between both severity and duration of psoriasis and the development of PsA, yet other reports have suggested that the incidence of PsA remains constant after the initial diagnosis of psoriasis( 10 – 12). Nevertheless, on a population level the incidence of PsA is steadily increasing across all age groups( 13). To date, predictors for development of PsA have been identified, including severe psoriasis, nail involvement, low educational level, and uveitis, few of which are modifiable( 14). The incidence of PsA is highest among patients in their fifth decade, the male-to-female ratio is 1:1, and the disease is most frequent among Caucasians( 13, 15). Obesity is a reasonably well-established risk factor for PsA among patients with psoriasis, yet while some studies have suggested that smoking, alcohol use, and the anatomical location of psoriasis may also be risk factors, the evidence for these are scarce and there is a need for additional studies to predict development of PsA in patients with psoriasis( 16). We therefore examined the effect of duration of psoriasis on the risk of developing PsA in a nationwide cohort in Denmark.
METHODS Data sources and study population
Study approval was obtained from the Danish Data Protection Agency( ref. 2007-58-0015, int. ref. GEH-2014-018, I-Suite 02736). Danish register-based studies are exempted from ethics committee and institutional review board approvals. We conducted and reported the study in accordance with the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology( 17). All records, including source codes for the present study, are kept at secured and encrypted servers held by Statistics Denmark.
Individual-level information was linked from nationwide administrative registers using a unique and unambiguous personal identification number that all Danish residents are assigned at birth or migration. The Civil Registration System( 18) contains information on sex, date of birth, and updated information on vital status and emigration, thus minimizing loss to follow-up. All inpatient and outpatient( ambulatory) hospital consultations are recorded doi: 10.2340 / 00015555-2912 Acta Derm Venereol 2018; 98: 546 – 550
This is an open access article under the CC BY-NC license. www. medicaljournals. se / acta Journal Compilation © 2018 Acta Dermato-Venereologica.