Microstomia is associated with functional impairment and is a poor prognostic factor in systemic sclerosis - a single center observational study with survival analysis.

Background: Objectives were to assess the mouth opening ability (MOA) among patients with systemic sclerosis (SSc) in comparison to a healthy control population. The impact of microstomia (decrease in any of the MOA parameters) on physical performance and long-term survival was also investigated.

Methods: Interincisal (ID), interlabial (LD), the intercommissural distances at both opened mouth and closed mouth (OW, CW) and the oral area (OA) and circumference (OC) all were assessed in 131 SSc patients. Microstomia was defined based on the oral aperture values of a healthy control group (n = 63) with similar median age and sex distribution. Tests evaluating functional performance were performed. Survival analysis by univariate and multivariate Cox regression analysis was performed.

Results: Microstomia was present in 56.5% of the entire SSc cohort. Patients with microstomia had higher number of contractures compared to those with preserved oral aperture parameters (median 10 vs. 7, p < 0.01). LD, OA and OC correlated negatively with the number of joint contractures, both in the entire SSc cohort and separately in the diffuse (dcSSc) and limited cutaneous subsets (lcSSc), (rho: between - 0.267 and - 0.516, p < 0.05). Reduced ID was associated with worse Health Assessment Questionnaire Disability Index (HAQ-DI) only in dcSSc while reduced LD was linked to increased HAQ-DI scores in both SSc subsets. Decreased OA upon enrollment was associated with an increased risk in mortality by multivariate Cox regression analysis (HR: 2.74; 95% CI, 1.15-6.53).

Conclusions: Microstomia was associated with joint damage, and higher overall disability based on HAQ-DI. Interlabial distance was a beneficial, convenient measurable parameter to characterize oral aperture. Oral area was an independent poor prognostic factor regarding long-term survival.