Changes in disability and their relationship with skin thickening, in diffuse and limited cutaneous systemic sclerosis: a retrospective cohort study

Objective. The burden of disability associated with systemic sclerosis (SSc) is being increasingly recognised. Our aim was to test the hypothesis that changes in functional ability over time differ between patients with limited (lcSSc) and diffuse cutaneous (dcSSc) subtypes, and that in patients with dcSSc (but not in those with lcSSc) these changes correlate with skin thickening. Methods. This was a retrospective analysis of data collected prospectively between 2005 and 2016 at a single centre. Data recorded at annual review visits included the modified Rodnan skin score (mRSS) and the Health Assessment Questionnaire Disability Index (HAQ-DI). The yearly rates of mRSS and HAQ-DI change were assessed by individual linear regressions, and those gradients were compared between disease groups (lcSSc/dcSSc) for each of early/late disease (less or greater than 5 years duration). Results. 402 patients (110 dcSSc, 292 lcSSc) were included, mean length of follow-up 5.5 years (SD 3.5). Mean baseline HAQ-DI was 1.4 in dcSSc and 1.2 in lcSSc. In dcSSc, an increase in mRSS was associated with worsening disability (ρ=0.36 and p=0.004) during early but not during late disease (ρ=0.12 and p=0.331). In lcSSc, changes in mRSS were not associated with changes in disability for early (ρ=-0.15 and p=0.173) or late disease (ρ=0.10 and p=0.137).Conclusion. These findings confirm high disability in patients with SSc. A relationship between HAQ-DI and mRSS (worsening mRSS associated with increasing disability) was found only in patients with early dcSSc, suggesting that in other subgroups of patients other factors play the major role.