Background Skin disease predates the onset of psoriatic arthritis (PsA) in about 60% of cases . The transition from skin disease to joint involvement is only partially characterized. Erosive changes and new bone formation are both typical characteristics of the PsA disease spectrum.
Objectives To explore whether patients with cutaneous psoriasis (PSO), without clinical history and presence of synovitis and no fulfillment of the CASPAR criteria at any time, show early changes of the periarticular bone that are typical of PsA.
Methods PSO patients and healthy subjects (HS) underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) of the dominant hand. Examination focused on the following regions of interest: metacarpal head and phalangeal base of the MCP joints 2 and 3 (Fig.1A). Erosions, defined as breaks in the cortical shell within the joint and visible in two planes, were assessed by frequency and volume (mm3) . Osteophytes, defined as bony protrusions emerging from the cortical shell and located in the periarticular region (Fig.1B), were assessed by frequency and maximal height (mm, i.e. distance between the highest surface of the lesion and the original surface of the cortical bone) . The study was conducted upon approval by the local ethic committee and the National Radiation Safety Agency (BfS). Patients participated after signing informed consent.
Results Images were acquired from 55 PSO patients (mean age 49.5±11.5 years, 36.4% female) and 47 HS (mean age 45.8±13.0 years, 48.9% female). Mean age and sex distribution were comparable between groups. PSO patients had mean disease duration of 15.2±15.4 years and mean PASI score of 6.2±8.0. The most prevalent subtype was psoriasis vulgaris (73%), while nail psoriasis was present in 51% and scalp involvement in 29%. By HR-pQCT, 27 erosions were identified in PSO patients and 18 in HS. The most frequently involved compartment was the metacarpal head 2 for both groups. No differences were found with respect to the mean volume of the erosions in the two groups. With regard to osteophytes, 306 were identified in the PSO group and 138 in the HS. Again the most frequently involved site was the metacarpal head 2 for both groups. Notably PSO patients showed larger osteophytes compared to the HS in each region of interest. For the metacarpal head 2 the mean size accounted for 1.7±0.8 vs. 1.2±0.5 mm respectively, t(77.9)=3.53 p=0.001. For the metacarpal head 3 it was 1.2±0.6 and 0.8±0.3 mm, U=280.0, Z= -3.256, p=0.001. In the phalangeal base 2 the PSO patients showed a mean size of 1.3±0.7 mm, and the HS of 0.7±0.3 mm (t(52.1)=4.23, p<0.001). In the phalangeal base 3 mean values accounted for 1.2±0.7 mm and 0.8±0.2 respectively (t(43.7)=3.20, p=0.003).
Conclusions HR-pQCT analysis of the bone microstructure indicates that PSO patients without a history of arthritis seem to show more osteophytes than healthy subjects in the explored regions. New periarticular bone formation could be an early expression of altered bone remodeling previous to the onset of PsA.
McGonagle D, et al. Ann Rheum Dis. 2011 Mar; 70(S1): i71-6
Albrecht A, et al. Ann Rheum Dis. 2013;72:1351-7
Finzel S, et al. Ann Rheum Dis. 2013;72:1176-81
Disclosure of Interest None declared