Clinical utility of hypo- and hyperpigmentation of skin in diffuse cutaneous systemic sclerosis

Cutaneous involvement is an early manifestation of systemic sclerosis (SSc). Localized areas of 'salt and pepper skin' (S&P) may develop. We hypothesize that S&P skin occurs frequently in diffuse cutaneous (dc) SSc which can be used in its early diagnosis and may correlate with joint contractures.

Sixty-five patients were recruited for this study. The demographic profiles of SSc were ascertained from hospital records. These patients fulfilled the 2013 American College of Rheumatology/European League Against Rheumatism classification criteria. Patients were examined for skin pigmentary changes, modified Rodnan skin score (mRSS), telengiectasias, calcinosis, arthritis and joint contractures and pruritus.

Sixty-five patients (59 female) were recruited with median age of 62.87 years. Forty-four had limited cutaneous SSc, 16 dcSSc, five had scleroderma overlap syndrome. Multivariate stepwise logistic regression indicated that mRSS severity and the presence of contractures were independently (P < 0.05) associated with dcSSc. The strong positive association between S&P and mRSS severity may explain the non-significance of S&P in this analysis. If mRSS severity is not included in the logistic regression analysis, the presence of contractures and S&P (odds ratio = 15.1) show significant (P < 0.01) independent associations with the dcSSc subtype. S&P skin and pruritus were similar in patients with Scl-70 and anti-RNA polymerase antibodies. Anti-centromere antibodies were negatively associated with S&P (χ² = 7.89, P = 0.005).

Our study demonstrates strong association of S&P skin with dcSSc (69%), increased risk of pruritus and contractures. Its presence can be used as another clinical tool to diagnose dcSSc in early stages. Observing for S&P skin changes does not require much training.