Epidemiology of systemic sclerosis

Systemic sclerosis (SSc) is a multisystem auto-immune disease. The two main subtypes of SSc (limited and diffuse) typically have differing courses and prognoses. New classification criteria have been proposed to identify SSc in the earliest stages, before skin involvement. Over the past three decades, there has been an apparent increase in the incidence of SSc to approximately 20 per million, possibly due to improved diagnosis. The most extensively studied environmental associations of SSc are organic solvents and silica but no single risk factor has emerged. Recent genetic studies have identified new susceptibility factors including human leucocyte antigen (HLA) haplotypes and polymorphisms in immune regulatory genes. Despite earlier disease recognition and effective treatment for some of its complications, SSc still carries a high mortality, particularly due to cardiorespiratory complications. Although some predictors of organ involvement and outcomes have been identified, novel biomarkers are greatly needed. Due to low disease prevalence, large multicentre research collaborations are required.