Background Currently, the diagnosis and assessment of psoriatic arthritis (PsA) and psoriasis (PsO) skin lesions are mostly done by visual inspections, and when in doubt, supplemented by biopsies. Although PsA is primarily assessed by physical examination, the utility of ultrasound (US) is beneficial.
Objectives The aim of this proof of concept study was to determine the performance of ultrasound (using advanced imaging software applications) in assessing skin lesions and inflammation in selected PsA and PsO patients.
Methods A rheumatologist and dermatologist assessed the PsA and PsO patients respectively. PsA examination included the standard clinical joint assessments, and we thereafter evaluated the hands & wrists and symptomatic joints with US for synovitis & tenosynovitis (including nail beds & tendons). Blinded by the clinical results and treatment plans, the epidermal, dermal and subcutaneous tissue thicknesses of 2 of the most affected psoriasis lesions were US scanned using high frequency B-Mode, automated Color Doppler quantification (CDQ; measured over 4 seconds) and elastography applications (measuring lesion size, depth, hyperemia and tissue elasticity). The skin tissue adjacent to the psoriasis lesions, as well as the unaffected skin on the contralateral side (self-control) was measured.
Results A total of 270 skin depth measurements (2 of the most affected lesions, 3 intervals apart, at 3 different sites described above) of 5 PsA/PsO patients were analyzed. Epidermal thickness differed significantly between the adjacent and control tissue layers [F (2,27) =30.95, MSE =0.76, p<0.001]. Similar findings were evident for dermal thickness differences [F (2,27) =5.05, MSE =1.59, p=0.014]. In contrast and as expected, subcutaneous tissue thicknesses showed no significant differences. US using color Doppler revealed the presence of hyperemia in 80% of the examined lesions by CDQ resulted in flow averages ranging from 0.016–0.655 for minimum ratios to 0.103–0.241 for maximum ratios. Of these Doppler active lesions, 60% were echogenic (some with acoustic shadowing). Contrary, 20% of the psoriasis lesions showed no obvious Doppler activity, displaying reduced tissue stiffening on elastography (suggesting healed lesions). Two of 10 (20%) lesions showed no abnormal findings (soft on elastography) having no acoustic shadows, and low-level CDQ activity (minimum 0.016:0.034 and maximum 0.103:0.135 ratios). Ultrasound displayed the presence of synovitis, tenosynovitis, and nail-bed hyperemia together with altered microcirculation & hand psoriasis skin perfusion in PsA patients.
Conclusions Ultrasound metrics of skin tissue (plaque characteristics, tissue depth & elasticity, and Doppler activity quantification) has potential as a complementary measure for the clinical assessment of PsA and PsO.
Disclosure of Interest None declared