A sonographic spectrum of psoriatic arthritis: “the five targets”
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Ultrasound is a rapidly evolving technique that is gaining an increasing success in the assessment of psoriatic arthritis. Most of the studies have been aimed at investigating its ability in the assessment of joints, tendons, and entheses in psoriatic arthritis patients. Less attention has been paid to demonstrate the potential of ultrasound in the evaluation of skin and nail. The aim of this pictorial essay was to show the main high-frequency grayscale and power Doppler ultrasound findings in patients with psoriatic arthritis at joint, tendon, enthesis, skin, and nail level.
KeywordsPsoriatic arthritis Ultrasound Power Doppler Joint Tendon Enthesis Skin Nail
Psoriatic arthritis (PsA) is a chronic and heterogeneous inflammatory joint disease that occurs in 6–42% of patients with psoriasis . A variable spectrum of pathologic condition can be found in PsA patients including joint and tendon inflammation, enthesitis, new bone formation, severe osteolysis, and overlap of all of these . A common denominator is the skin psoriasis . Recently, the definition “psoriatic disease” has been proposed to encompass the involvement at different tissue and organ levels .
The continuous technological advances in the field of ultrasound (US) allowed the development of equipments provided with high and variable frequency probes and very sensitive power Doppler (PD), which permit both the detailed study (with resolution power of 0.1 mm) of morphostructural changes and the sensitive detection of blood flow even in small vessels of superficial tissues [5, 6, 7, 8]. Most of the studies have been aimed at investigating the ability of US in the assessment of joints, tendons, and entheses [9, 10, 11, 12, 13, 14, 15] in patients with PsA. Less attention has been paid to demonstrate the potential of US in the evaluation of skin and nail.
The aim of this pictorial essay was to show the main high-frequency grayscale US and PD findings in patients with PsA at joint, tendon, enthesis, skin, and nail level.
The US images illustrated in the present pictorial essay were obtained in a cohort of 30 patients with diagnosis of PsA, made by an experienced rheumatologist (RDA) according to the international criteria . Clinical examination aimed to detect tenderness and/or swelling at joints, tendons, and entheses level was performed by the same rheumatologist. Twenty of the 30 patients presented a skin involvement and eight patients an onychopathy, diagnosed clinically by an experienced dermatologist (GF), who moreover scored both Psoriasis Area and Severity Index (range between 8 and 20, median 12.4) and Nail Psoriasis Severity index (range between 2 and 8, median 3.5). The US examinations were performed by two experienced sonographers (MG and EF), using the following US systems: MyLab 70 XVG (Esaote Biomedica Genoa, Italy) equipped with 6–18 MHz broadband multifrequency linear transducer (axial resolution = 30 μm and lateral resolution = 60 μm) and Doppler frequency ranging from 7.1 to 14.3 MHz; Technos “Partner” System (Esaote Biomedica Genoa, Italy) equipped with 8–14 MHz multifrequency linear band transducer (axial resolution = 50 μm, lateral resolution = 80 μm) and Doppler frequency ranging from 8.3 to 12.5 MHz and Logiq 9 (General Electric Medical Systems, Milwaukee, WI, USA) equipped with 8–15 MHz multifrequency linear transducer (axial resolution = 10 μm, lateral resolution = 25 μm). The most representative images showing the main pathological findings were selected from the database of the three US machines used in this study.
The US examinations of musculoskeletal system were performed with multiplanar technique, at the clinically involved sites adopting the indications provided by the European League Against Rheumatism guidelines for musculoskeletal ultrasound in rheumatology .
During US examination of skin, representative US images were acquired at both the center and the margins of the psoriatic lesion and at the surrounding normal skin. Skin thickness varies among healthy subjects and depends on several aspects including the different areas of the body. Thus, the thickness of the normal skin surrounding the psoriatic lesion was used as reference for detecting the thickening of the epidermis and/or the dermis. The totality of US evaluations was insonated on both longitudinal and transverse scans and perpendicularly using an amount of gel, which avoids compression of the tissues under examination. All examinations were performed in both grayscale and PD technique in order to detect the morphostructural changes and the presence of abnormal blood flow, respectively. The PD settings for all examinations were standardized with a pulse repetition frequency of 750 Hz and a Doppler frequency between 7.5 and 14.3 MHz. In order to confirm that the PD signal represented real blood flow and not an artifact, the spectral Doppler was used. The study was conducted according to the Declaration of Helsinki, and informed consent was obtained from all patients.
Grayscale US pathological findings in the joints of patients with PsA
Homogeneous anechoic joint space widening 
Joint space widening with clusters of soft echoes (bushy and villous appearance) and/or homogeneous synovial thickening 
An intra-articular discontinuity of the bone surface that is visible in two perpendicular planes 
Last generation US equipment provides a detailed assessment of the entheseal morphostructural features. Thanks to the superficial location of the most frequently involved entheses, probes with high-frequency PD can be used, allowing for a sensitive assessment of the entheseal perfusion status.
The joint, tendon, enthesis, skin, and nail involvement has been described by the different subsets criteria as aspects to be considered in PsA [2, 22, 23, 24, 25]. Recently, the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) underlined the value of imaging findings in PsA, from both a dermatologic and rheumatic perspective .
In this way, there is a consistent body of evidence supporting both the role of US and its higher sensitivity over clinical examination in the diagnosis of synovitis, enthesitis, and tenosynovitis in PsA [9, 10, 11, 12, 13, 14, 15, 20, 21, 27, 28, 29, 30, 31, 32]. Relatively uncertain remains its potential in the assessment of skin and nail involvement in these patients.
To date, most of the studies assessing the role of US in psoriatic skin and nail have not used the latest generation of US equipment and have concentrate mainly on pathological findings using only the grayscale technique [7, 33, 34, 35, 36, 37, 38, 39, 40]. The images shown in this paper were acquired with “last generation” top quality US equipment provided with high and variable frequency probes and very sensitive PD.
Our results demonstrated that the increase of blood flow in psoriatic plaque and onychopathy, which is due to several dermovascularity changes such as elongation, dilatation, and twisting of the microvessels , can be easily detected by high PD frequency.
Considering the common pathogenesis between the angiogenesis of psoriatic plaque and synovial membrane , the US could be considered as a powerful method able to provide a widespread and more complete assessment of morphostructural changes and disease activity at different locations such as joint, tendons, entheses, skin, and nail in patients with PsA. Another interesting utility could be the monitoring of treatment at multiple targets, that despite the availability of “new generation” US machines, remains under investigated for this condition [42, 43, 44]. Recently, our group demonstrated the ability of US in monitoring of the psoriatic plaque in patients treated with tumor necrosis factor alpha antagonist therapy .
Additionally, from the joint US assessment point of view, we noted that the synovial pannus of PsA appears highly hyperemic respect to other chronic inflammatory conditions. It can easily be detected at the small joints level (distal and proximal interphalangeal joints, metacarpophalangeal and metatarsophalangeal joints) using probes with high PD frequency (>10 MHz). Its study results relatively difficult at the large joints level (such as shoulder, knee, and hip), and these, due to their anatomical depth (especially in obese patients), require low frequency probes which decrease the PD sensitivity.
In conclusion, the present report provides update pictorial evidence that high-resolution grayscale US and high-frequency PD allow a detailed assessment of the morphostructural changes and a sensitive detection of abnormal blood flow at multiple sites in patients with PsA. Studies aiming at investigating diagnostic value, validity issues including accuracy, and reproducibility are required to define the impact of these US findings in daily clinical practice.
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- 11.McGonagle D (2005) Imaging the joint and enthesis: insights into pathogenesis of psoriatic arthritis. Ann Rheum Dis 64(suppl 2):58–60Google Scholar
- 14.Wiell C, Szkudlarek M, Hasselquist M, Møller JM, Vestergaard A, Nørregaard J, Terslev L, Østergaard M (2008) Ultrasonography, magnetic resonance imaging, radiography, and clinical assessment of inflammatory and destructive changes in fingers and toes of patients with psoriatic arthritis. Arthritis Res Ther 10:402CrossRefGoogle Scholar
- 15.Fournié B, Margarit-Coll N, Champetier de Ribes TL, Zabraniecki L, Jouan A, Vincent V, Chiavassa H, Sans N, Railhac JJ (2006) Extrasynovial ultrasound abnormalities in the psoriatic finger. Prospective comparative power Doppler study versus rheumatoid arthritis. Joint Bone Spine 73:527–531CrossRefPubMedGoogle Scholar
- 17.Backhaus M, Burmester GR, Gerber T, Grassi W, Machold KP, Swen WA, Wakefield RJ, Manger B (2001) Working Group for Musculoskeletal Ultrasound in the EULAR Standing Committee on International Clinical Studies including Therapeutic Trials. Guidelines for musculoskeletal ultrasound in rheumatology. Ann Rheum Dis 60:641–649CrossRefPubMedGoogle Scholar
- 22.Bennett RM. Psoriatic arthritis (1979). In: McCarty DJ (ed), Arthritis and related conditions. Philadelphia: Lea & Febiger, p. 645Google Scholar
- 23.Vasey FB, Espinoza LR (1984) Psoriatic arthritis. In: Calin A (ed) Spondyloarthropathies. Grune, Orlando, pp 151–185Google Scholar
- 32.Filippucci E, Aydin SZ, Karadag O, Salaffi F, Gutierrez M, Direskeneli H, Grassi W. Reliability of high-resolution ultrasonography in the assessment of Achilles tendon enthesopathy in seronegative spondyloarthropathies (2009). Ann Rheum Dis (Epub ahead of print)Google Scholar
- 47.Wakefield RJ, Balint P, Szkudlarek M, Filippucci E, Backhaus M, D’Agostino MA, Sanchez EN, Iagnocco A, Schmidt WA, Bruyn GA, Kane D, O’Connor PJ, Manger B, Joshua F, Koski J, Grassi W, Lassere MN, Swen N, Kainberger F, Klauser A, Ostergaard M, Brown AK, Machold KP, Conaghan PG (2005) OMERACT 7 Special Interest Group. Musculoskeletal ultrasound including definitions for ultrasonographic pathology. J Rheumatol 32:2485–2487PubMedGoogle Scholar
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