Response to 'Ultrasound characterization of cutaneous ulcers in systemic sclerosis'

The role of ultrasound in systemic sclerosis: On the cutting edge to foster clinical and research advancement

Ultrasound has been widely explored in systemic sclerosis in the clinical and research settings. Ultrasound allows a non-invasive and ionising radiation-free 'window' into this complex disease and is well-suited to repeated examinations. Ultrasound provides novel insights into the pathogenesis and measurement of disease in systemic sclerosis, including early (preclinical) internal organ involvement. The purpose of this review is to describe the role of ultrasound to foster clinical and research advancements in systemic sclerosis relating to (1) musculoskeletal, (2) digital ulcer, (3) lung disease and (4) skin disease. We also highlight unmet needs which much be addressed for ultrasound to assume a central role in systemic sclerosis clinical care and research.

The Updated Role of Ultrasound in Assessing Dermatological Manifestations in Systemic Sclerosis

Systemic sclerosis (SSc), an autoimmune connective tissue disease, characterized by skin fibrosis, increased dermal thickness and microvascular involvement. Fibroblasts and myofibroblasts deposit excessive amounts of collagenous and non-collagenous extracellular matrix components in the skin. This leads to microvascular abnormalities and Raynaud's phenomenon, with painful digital ulcers (DU) at the fingertips adding to patient discomfort. The skin involvement and severity in SSc was evaluated by the Modified Rodnan skin score (mRSS). Although high-frequency ultrasound (HUS) has been widely researched in the study of skin thickness and DU in SSc, its adoption into clinical practice is not yet common. However, novel insights into the still relatively unknown disease pathogenesis in SSc and its evaluation may be provided by HUS, including early (pre-clinical) skin involvement. It may also be useful in both the evaluation and follow-up of DU. Indeed, it is a non-invasive, safe, inexpensive and reproducible method able to assess not only SSc patients' cutaneous structural changes, but also their vascular system changes. Moreover, several recent studies have reported that elastosonography (ES) is of use when investigating skin involvement in systemic sclerosis. This review aims at providing information as to role HUS and ES play in research advancements and the clinical perspectives in the evaluation of skin thickness and DU in SSc patients.

Ultrasonographic imaging of systemic sclerosis digital ulcers: A systematic literature review and validation steps

INTRODUCTION/BACKGROUND

Skin ulcers are a complex array of clinical manifestations of systemic sclerosis (SSc) and are often difficult to treat. However, the definition of SSc-skin ulcers has to date not been promising, demonstrating poor reliability and accuracy. There are emerging data that ultrasound has significant potential to evaluate SSc-skin ulcers.

OBJECTIVE

To perform a systematic literature review (SLR) to understand the degree to which ultrasound of SSc skin ulcers has been validated according to OMERACT criteria.

METHODS

In a SLR, we investigated the Cochrane Library, Web of Science and Pubmed databases for manuscripts from inception to 1st April 2020. Inclusion and exclusion criteria included manuscripts on SSc patients aged over 16 years, performing SSc-related skin ulcer evaluation with ultrasound machines. Papers on animal model, diseases other than SSc, venous ulcers were excluded. Data extraction used a uniform case report form which collected data on patient demographics, disease activity, description of the ultrasound machine and procedures and the degree to which domains of validity were fulfilled. Manuscript evaluation and extraction was performed by two independent assessors, with a third author being consulted in case of disagreement.

RESULTS

amongst 308 manuscripts that were identified, 6 published manuscripts/ posters fulfilled the inclusion/exclusion criteria and were extracted. Face validity was found. Three studies developed an US definition of SSc-ulcers across patients (content validity); one study evaluated the concordance between US image and clinical assessment. Criterion validity was shown by one study and ultrasound detected improvement (sensitivity to change) of SSc-skin ulcer in response to therapy. Feasibility was demonstrated by US use for skin ulcers in multiple settings (the 6 manuuscripts/posters).

CONCLUSION

This systematic literature review shows that ultrasound for skin ulcers in SSc has been partially validated. It has face, content, criterion validity, responsiveness and reasonable feasibility. Further validation for construct validity, reliability and discrimination is required.

Imaging digital arteries in systemic sclerosis by tomographic 3-dimensional ultrasound

Objective methods are needed to quantify digital artery disease in systemic sclerosis (SSc) for clinical trials of vascular therapies. Our primary aim was to examine feasibility of a novel tomographic three-dimensional-(3-D) ultrasound (tUS) with high-frequency ultrasound (HFUS) or ultra-high-frequency ultrasound (UHFUS) to assess the digital arteries in patients with SSc compared to healthy controls. A secondary objective was to compare the total wall volume (TWV) as a measure of intimal/medial thickness. Eighteen patients with a confirmed diagnosis of SSc were studied by tUS HFUS (17.5 MHz, n = 10) or tUS UHFUS (48 and 70 MHz, n = 8) with equal numbers of healthy controls of similar age and gender. The majority of patients had limited cutaneous SSc and were representative of a spectrum of digital vasculopathy, with over half (n = 6 HFUS and n = 5 UHFUS) having previous digital ulceration. Over half were receiving oral vasodilatory therapy. TWV was measured in both digital arteries of the middle finger bilaterally. At least, two digital arteries could be identified at 17.5 MHz in all patients and healthy controls. Whereas, at least two digital arteries could be identified in relatively fewer patients compared to healthy controls using 48 MHz (n = 6 and 10) and especially 70 MHz (n = 4 and 10) UHFUS. The median difference in TWV between patients and healthy controls was -6.49 mm³ using 17.5 MHz, 1.9 mm³ at 48 MHz, and -0.4 mm³ at 70 MHz. tUS using UHFUS is a feasible method to measure TWV of digital arteries in SSc. Transducer frequency plays an important factor in successful digital artery measurement, with 48 MHz being the optimal frequency.

Raynaud phenomenon and digital ulcers in systemic sclerosis

Raynaud phenomenon is a symptom complex caused by impaired digital perfusion and can occur as a primary phenomenon or secondary to a wide range of underlying causes. Raynaud phenomenon occurs in virtually all patients with systemic sclerosis (SSc) and is often the earliest clinical manifestation to occur. Careful assessment is required in patients with Raynaud phenomenon to avoid missing secondary causes such as SSc. Digital ulcers are a painful and disabling visible manifestation of digital vascular injury in patients with SSc. Progress has been made in the classification and assessment of digital ulcers and in understanding ulcer pathogenesis, and there are a wide range of treatments available to both prevent and heal digital ulcers, some of which are also used in Raynaud phenomenon management. In this Review, the assessment of patients with Raynaud phenomenon is discussed, including 'red flags' that are suggestive of SSc. The pathogenesis, classification and assessment of SSc-associated digital ulcers are also covered, alongside an overview of management approaches for SSc-associated Raynaud phenomenon and digital ulcers. Finally, unmet needs are discussed and the concept of a unified vascular phenotype in which therapies that affect the vasculature to support disease modification strategies is introduced.