Subhydroxylated collagen in scleroderma

In sclerodermal skin, the values for proline (Pro), hydroxyproline (Hyp) and hydroxylsine (Hyl) are lower than in normal skin. The molar ratio Hyp to Hyl is lowered. The molar ratio Pro to Hyp was found to be elevated, while that of Pro to Hyl was like that of normal skin. It was concluded that in slceroderma the hydroxylation of Pro to Hyp is incomplete, resulting in an abnormal collagen.