|Year : 2017 | Volume
| Issue : 4 | Page : 192-193
Quantitating skin thickness in systemic sclerosis: The way ahead
Shefali Sharma, Aadhaar Dhooria
Department of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||16-Nov-2017|
Department of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh - 160 012
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sharma S, Dhooria A. Quantitating skin thickness in systemic sclerosis: The way ahead. Indian J Rheumatol 2017;12:192-3
Scleroderma or skin thickening is the most characteristic feature of systemic sclerosis (SSc) and also the source of greatest concern to the patient. Some of the earliest descriptions in modern medical literature date back to the late 19th century. While the rheumatologist tends to focus on interstitial lung disease (ILD) and pulmonary hypertension (PAH) owing to their impact on mortality, the patient is primarily concerned by the hide-like appearance of the skin and ensuring functional and cosmetic limitations.
The quest for developing tools to accurately measure skin thickness is not recent. It was in 1979 that Rodnan and his research assistants described a system for measurement of skin involvement in SSc. They performed skin biopsies from extensor aspect of forearm in SSc patients and weighed water and hydroxyproline content in these biopsies. They reported a close correlation between clinical estimation of skin thickening and weight of core biopsies. These findings led to the development of the Rodnan skin score, its subsequent modifications have formed the backbone of SSc research to date. However, it has been realized for some time now that the modified Rodnan skin score or modified Rankin Scale score (mRSS) suffers from significant interobserver as well as intraobserver variation thereby limiting its utility for comparison across centers and trials.
The need for assessing skin thickness reliably and the limitations of the mRSS have led to the use of newer modalities such as the elastometer (linear extension), durometer (skin hardness), plicometer (measurement of skin folds), vesmeter (viscosity, elasticity, and softness), twistometer (skinn rotation), and cutometer (skin suction). These mechanical modalities are more objective than mRSS, however, most of them have limited utility in measuring skin thickness over the bony prominences such as fingers. Furthermore, the ability to differentiate between thickened skin, subcutaneous tissue, and tethered skin is doubtful.
Ultrasound (US) is being widely used in rheumatology, especially rheumatoid arthritis and it is no surprise that its use is being advocated for measuring skin thickness in SSc. High frequency US was tried but consistent results were not obtained across trials. Interest in HFUS seems to be fading and it has been replaced by elastosonography including shear wave elastography (SWE). Optical Coherence Tomography (OCT), used primarily in ophthalmology, is another exciting modality meriting further research.
In this context, the findings of a study by Wakhlu et al. in this issue of the journal describing the use of SWE for quantitating skin thickness in SSc patients are interesting. The minimal intraobserver variation is a welcome improvement over the mRSS. SWE may help to identify early skin changes in these patients. However, the correlation between mRSS and SWE remains modest. Furthermore, SWE failed to differentiate between SSc patients and healthy controls over the chest, abdomen, thighs, and legs. Another issue is the time required to perform SWE at each of 17 sites as described in the mRSS which may preclude its use in routine clinical practice.
Two issues plague the development of new methods to quantitate skin involvement in these patients. First, the gold standard, mRSS, is prone to significant inter- and intra-observer variability complicating the validation of new techniques using the same. The correlation with skin biopsies though tempting, may not be practically feasible. Second, these methods including the mRSS are notoriously insensitive in measuring the change in skin thickness in response to treatment. While most of the research and clinical trials hover around the treatment of ILD and PAH in SSc patients, the skin also responds to the treatment given for these conditions and may sometimes be the only organ which responds to treatment. While SWE appears promising, its ability to measure the change in skin thickness remains unproven. We hope that future research will focus on measuring the change in skin thickness using SWE.
| References|| |
Rodnan GP, Lipinski E, Luksick J. Skin thickness and collagen content in progressive systemic sclerosis and localized scleroderma. Arthritis Rheum 1979;22:130-40.
Czirják L, Foeldvari I, Müller-Ladner U. Skin involvement in systemic sclerosis. Rheumatology (Oxford) 2008;47 Suppl 5:v44-5.
Abignano G, Del Galdo F. Quantitating skin fibrosis: Innovative strategies and their clinical implications. Curr Rheumatol Rep 2014;16:404.
Wakhlu A, Chowdhury AC, Mohindra N, Tripathy SR, Misra DP, Agarwal V. Assessment of extent of skin involvement in scleroderma using shear wave elastography. Indian J Rheumatol 2017. [doi: 10.4103/injr.injr_41_17].