Noninvasive measurement of skin autofluorescence is increased in patients with systemic sclerosis: an indicator of increased advanced glycation endproducts?

OBJECTIVE: Skin autofluorescence noninvasively assesses expression of advanced glycation endproducts and therefore potentially the presence of oxidative stress that is implicated in the pathogenesis of systemic sclerosis (SSc). We investigated whether autofluorescence was increased in patients with SSc, primary Raynaud's phenomenon (RP), and morphea as compared to healthy controls. METHODS: Measurements of autofluorescence were made at 5 upper limb sites in 16 healthy controls, 16 patients with diffuse cutaneous SSc (dcSSc), 15 with limited cutaneous SSc (lcSSc), 15 with primary RP, and 13 with morphea. For patients with morphea, additional measurements were made at the affected and an adjacent unaffected site. RESULTS: Autofluorescence was significantly increased in patients with dcSSc but not lcSSc as compared to controls at the proximal phalanx [dcSSc median 0.15, interquartile range (IQR) 0.10-0.24, vs control 0.10, IQR 0.07-0.13; p = 0.014], dorsum of the hand (dcSSc 0.17, IQR 0.11-0.36, vs control 0.12, IQR 0.09-0.17; p = 0.031), the wrist (dcSSc 0.22, IQR 0.13-0.33, vs control 0.13, IQR 0.09-0.18; p = 0.005), and forearm (dcSSc 0.19, IQR 0.12-0.47, vs control 0.14, IQR 0.10-0.16; p = 0.022). There was a trend for autofluorescence to be increased in patients with lcSSc and at morphea sites, compared to noninvolved skin. CONCLUSION: Autofluorescence is increased in patients with dcSSc compared to primary RP and to healthy controls. This suggests increased oxidative stress and the potential for autofluorescence as a biomarker.