Background and objectives: Systemic sclerosis (SSc) is a connective tissue disease characterized by microvascular changes and fibrosis of the skin and internal organs. Increased skin thickness proximal to the metacarpophalangeal joints is the single major diagnostic criterion. The aim of this study was to evaluate high frequency (20 MHz) ultrasound for the assessment of skin thickness in patients with SSc of different disease durations.
Methods: Skin thickness was measured with high frequency (20 MHz) ultrasound equipment (Dermascan) in 41 patients with SSc (23 women and 18 men) and in 41 controls. Twenty-five patients had limited cutaneous systemic sclerosis (ISSc), 12 had diffuse cutaneous systemic sclerosis (dSSc) and 4 had suspected SSc.
Results: Skin thickness of the forearm was inversely correlated to disease duration. Compared to controls, skin thickness was increased over the proximal phalanx of the right second finger and over the forearm in patients with a disease duration of 2 years or less. Assessments of skin thickness in 10 controls by 2 independent investigators showed an inter-observer variability of 1.0% for the proximal phalanx and 0.0016% for the forearm. Patients whose ultrasound showed increased skin thickness on the hand and forearm also had thickened skin by palpation.
Conclusion: High frequency (20MHz) ultrasound is a feasible method for measuring skin thickness in SSc, and may be useful for diagnosis, long-term follow-up, and assessment in therapeutic studies.