Early Accrual of Organ Damage in Systemic Sclerosis: Rationale for Development of a Disease Damage Index

Abstract

Introduction Systemic sclerosis (SSc) is characterized by irreversible organ damage rather than fluctuating disease activity. However, there is no validated measure of damage in SSc. We aimed to quantify the accrual of organ damage in patients with early SSc. Methods Patients enrolled in the Australian Scleroderma Cohort Study with less than 2 years of SSc since the onset of the first non-Raynaud's symptom were included. Organ damage was defined by a group of six experts as substantial and permanent loss of organ function due to SSc. Results We identified 278 patients with early SSc. Among these, 38% had diffuse SSc. Damage was more common in the diffuse than in the limited disease subtype in the skin/musculoskeletal (75% vs. 25.2%, p<0.001) and lung (31.4% vs. 19.9%, p = 0.035) domains at year seven. The rates of damage accrual were highest in the skin/musculoskeletal, gastrointestinal and respiratory systems at year two (29.1%, 18.7%, 14.4%), increasing at year five (41.4%, 30.6%, 21.2%) and declining thereafter to year seven (43.9%, 32.7%, 23.0%). In particular, there was early accrual of damage due to joint contracture (22.3%), gastrointestinal dysmotility (11.5%) and pulmonary fibrosis with forced vital capacity <70% predicted (9.7%) at year two. The highest accrual rate of organ-specific damage from years two to seven was seen in fecal incontinence followed by proximal muscle weakness and pulmonary fibrosis. Conclusions Substantial accrual of organ damage occurs early in the course of disease, particularly in diffuse SSc. This provides the rationale for the development of a SSc damage index.