Skin fibrosis is the predominant feature of SSc and arises from excessive extracellular matrix deposition. Glycosaminoglycans are macromolecules of the extracellular matrix, which facilitate Na+ accumulation in the skin. We used 23Na-MRI to quantify Na+ in skin. We hypothesized that skin Na+ might accumulate in SSc and might be a biomarker for skin fibrosis.Methods.
In this observational case-control study, skin Na+ was determined by 23Na-MRI using a Na+ volume coil in 12 patients with diffuse cutaneous SSc and in 21 control subjects. We assessed skin fibrosis by the modified Rodnan skin score prior to 23Na-MRI and on follow-up 12 months later.Results.
23 Na-MRI demonstrated increased Na+ in the fibrotic skin of SSc patients compared with skin from controls [mean (s.d.): 27.2 (5.6) vs 21.4 (5.3) mmol/l, P < 0.01]. Na+ content was higher in fibrotic than in non-fibrotic SSc skin [26.2 (4.8) vs 19.2 (3.4) mmol/l, P < 0.01]. Furthermore, skin Na+ amount was correlated with changes in follow-up modified Rodnan skin score (R2 = 0.68).Conclusions.
23 Na-MRI detected increased Na+ in the fibrotic SSc skin; high Na+ content was associated with progressive skin disease. Our findings provide the first evidence that 23Na-MRI might be a promising tool to assess skin Na+ and thereby predict progression of skin fibrosis in SSc.