Systemic sclerosis (SSc) is a generalized disorder of small arteries, microvessels and connective tissue, characterized by fibrosis and vascular obliteration in the skin and organs, particularly the lungs, heart, and digestive tract. There are two main subsets of SSc: diffuse cutaneous SSc (dcSSc) and limited cutaneous SSc (lcSSc) (see these terms). A third subset of SSc has also been observed, called limited Systemic Sclerosis (lSSc) or systemic sclerosis sine scleroderma (see these terms).

Distance between the commissures of the mouth more than 2 SD below the mean. Alternatively, an apparently decreased width of the oral aperture (subjective).