High-frequency ultrasound of skin involvement in systemic sclerosis reflects oedema, extension and severity in early disease

Objective. The aim was to compare skin assessment by palpation and by high-frequency ultrasound in patients with SSc with disease duration < 2 yrs. Methods. Skin thickness and skin echogenicity were measured by 20 MHz ultrasound at five different anatomical sites in 106 individuals within 2 yrs from the first non-Raynaud's symptom and compared with the modified Rodnan skin score (mRss). Results. The patients with short disease duration were characterized by high skin thickness and low skin echogenicity, which correlated inversely, reflecting oedema. Patients with diffuse skin involvement displayed higher skin thickness and lower skin echogenicity than did patients with limited skin involvement. The ultrasound measurements correlated to the local mRss from the corresponding anatomical region and also to the total mRss. However, there was a considerable overlap in both skin thickness and skin echogenicity between different local mRss at all five anatomical sites. Skin involvement of the chest could be detected earlier by ultrasound than by palpation. Conclusion. In SSc patients with short disease duration, high-frequency ultrasound can identify the oedematous phase that may precede palpable skin involvement and may thus be useful to identify patients with diffuse skin involvement very early in the disease process. Ultrasound measurements also reflect the severity of the overall skin involvement.