Systemic sclerosis – a multi-purpose use of ultrasound

Sysyemic sclerosis (SSc) is a chronic connective tissue disease characterized by multi-organ involvement. In its variants, SSc may affect the skin, vessels, the heart, joints and the lungs. As such, it is potentially available for ultrasound examination in a wide field of applications.

With the most modern linear high-frequency transducers, it has become feasible to examine the skin in patients with SSc. US makes it possible to measure the thickness of the skin and subcutaneous tissue thereby helping determine the potential skin involvement and its range, and differentiate the localized from diffuse forms of SSc⁽¹⁾. Moreover, the examination of dermal thickness and echogenicity may be helpful in stratifying SSc into the edematous, fibrotic and atrophic phases of skin involvement⁽²⁾. Elastosonography, a method combining the assessment of ultrasound and elastic properties of the tissue, is also shown to be a promising technique in SSc⁽³⁾.

Raynaud phenomenon and vascular involvement in SSc may be the primary events, even preceding skin affection. The assessment of the vessels is therefore of cardinal significance in SSc. A Doppler analysis of flow in patients suspected of SSc may reveal if Raynaud phenomenon is of primary or secondary character⁽⁴⁾. The anatomical features of vessels may also help in the analysis of Raynaud phenomenon⁽⁵⁾. Furthermore, as atherosclerosis is more prevalent in patients with SSc, the assessment of carotid plaques with US⁽⁶⁾ may induce earlier prophylaxis in this group of patients. This assumption is strengthened by more frequent subclinical heart involvement in patients with SSc compared with healthy controls, as assessed with echocardiography⁽⁷⁾, yet another application of US in this disease.

In the rheumatologic world, it is obviously the musculoskeletal system that receives the most attention. And it is also like that in rheumatology-related US. Pain in the musculoskeletal system is frequently reported in patients with SSc. Until recently, it has been considered neither to be inflammatory nor leading to erosive joint disease. US supports though that the reason for pain can be detected and visualized. In studies comparing patients with SSc, rheumatoid arthritis (RA) and healthy controls, it has been shown that inflammatory joint changes occur as often as in joints of patients with RA⁽⁸⁾. Synovial proliferation, joint effusion and tendinitis were reported, and only Doppler signal and erosive joint disease were more frequent in patients with RA. In a study by Chitale et al., US findings in the hands of patients with SSc were compared with magnetic resonance imaging (MRI)⁽⁹⁾. The latter showed both more inflammatory changes than US and bone erosions, which were not detected with US. Tendon involvement was assessed in a study by Elhai et al. and signs of tendinitis were more frequent in patients with SSc in comparison with RA patients⁽¹⁰⁾. Another study by Cuomo et al. also presented characteristic features of tendon and retinaculum involvement showing a hyperechoic pattern⁽¹¹⁾.

In many SSc patients, interstitial pulmonary fibrosis (IPF) is a significant manifestation of the disease and a frequent cause of death. The method of choice for assessment and follow-up of IPF is high-resolution computed tomography (HRCT). The need for frequent assessments and the increasing radiation dose of SSc patients with lung affection makes the use of US, with a potential support of HRCT, particularly attractive in long-term monitoring as a non-radiation method. A significant correlation of findings in US, HRCT score and diffusion capacity of the lungs to carbon monoxide test in a study by Tardella et al.⁽¹²⁾, as well as other authors^{(13, 14)}, makes the possibility feasible. The elementary lesions in US assessment of patients with IPF are B-lines, i.e. vertical reverberation artifacts, also called comet tails, generated by the reflection of the US beam from thickened subpleural interlobular septa detectable in the lung intercostal spaces.

But still, the skin is the most dominant and frequently affected organ in SSc.

The authors of the paper in “Journal of Ultrasonography” deal with an aspect of SSc that is seldom investigated⁽¹⁵⁾. Grzegorz Pracoń et al. report on characteristic ultrasound features of hydroxyapatite deposits in a finger of a patient with limited SSc. It is an original finding which, when applied in practice, may lead to a quick surgical intervention and alleviation of the patient's symptoms.

The present study, seen in relation to the available research results, stresses the need for further and more detailed assessment of patients with SSc in the hope of quicker diagnosis, detecting complications and potential monitoring of the disease and its treatment.