Natural history of systemic sclerosis and the assessment of disease activity, severity, functional status, and psychologic well-being

The natural history of systemic sclerosis (SSc) is best understood by dividing patients into those who have diffuse cutaneous involvement or limited cutaneous involvement; each of these subsets can be further divided into early and late disease. Each of these four stages has characteristic clinical and laboratory features. Findings that are typical of inflammation (eg, tendon friction rubs, carpal tunnel syndrome) appear in early disease, whereas those that represent vascular and other organ structural changes (eg, joint contractures, telangiectasias, calcinosis) occur predominantly in late disease. Preliminary methods to measure SSc activity and damage have been published but require external validation and refinement. Among patient-completed instruments that assess functional status, the disability index of the Health Assessment Questionnaire is the most widely used and has face and construct validity, reliability, and sensitivity to change and is an accurate predictor of survival.