High frequency ultrasound: a novel instrument to quantify granuloma burden in cutaneous sarcoidosis

Background: As is the case for many skin diseases, cutaneous sarcoidosis does not currently have an objective measure of disease burden to establish disease severity and response to treatment. The disease has traditionally been assessed by visual skin changes, including induration and erythema; however, such assessments may fail to quantify the total skin granuloma burden, as the majority of the granulomatous inflammation may lie deep within the dermis and not be reliably detected by sight or palpation. Objectives: The purpose of this pilot study is to evaluate the feasibility of high frequency ultrasound as an objective measure of granuloma burden in cutaneous sarcoidosis and to compare high frequency ultrasound to a previously validated clinical instrument Cutaneous Sarcoidosis Activity and Morphology Instrument (CSAMI) and histopathology evaluation. Results: A strong correlation was observed between the mean brightness of high frequency ultrasound images and both the lesional CSAMI score (Spearman’s rho: 0.9710, p=0.0012) and percent of dermis with granulomas histopathology (Spearman’s rho: 0.8407 p=0.0361).  Conclusions: These results confirm high frequency ultrasound is a valid, objective measure of granuloma burden in cutaneous sarcoidosis and represents a novel, non-invasive measure of disease severity that correlates to the previously validated CSAMI clinical severity score and histopathology evaluation.