Background/Purpose: SSc is characterized by vasculopathy that precedes fibrosis and progresses to end-stage vascular manifestations such as malnutrition due to gastro-intestinal tract (GIT) involvement. Clinical management of SSc is a challenge because of limited information on the underlying pathophysiology. In this preliminary study, we aimed to determine if there were differences in sublingual microvascular health in SSc patients with/without sublingual frenulum abnormalities. We also examined the association between microvascular health and GIT scores in a pooled subset of patients.

Methods: Twenty-four patients fulfilling the 2013 ACR/EULAR classification criteria for SSc were recruited from the SSc clinic at the University of Utah.  Patients had their sublingual frenulum assessed as previously described by our group and completed the GIT 2.0 validated questionnaire.  Patients were grouped according to absence/presence of sublingual frenulum thickening/shortening (Fren-/Fren+, respectively).  The Glycocheck videomicroscopic sublingual device was used to image the sublingual frenulum in SSc patients.  This device is equipped with software that identifies > 3000 vascular segments and automatically starts when image quality is within acceptable range and automatically stops when a sufficient number have been collected. The device provides measurements of the number of well perfused vessels / mm^2 tissue surface, total number of vessels / mm^2 tissue surface, longitudinal vessel fraction that is filled with red blood cells (RBC), the fraction of vessels out of the total number that are well perfused (Dval/Dvot), RBC filled vessel density, penetration of red blood cells into the microvessel wall barrier region (perfused barrier region, PBR), and a MicroVascular Health score (MVH) which is a combined effect of these parameters (low MVH Score reflects low density and/or high PBR value = poor microvascular health). Additionally, a clinical feature of disease, SCTC GIT 2.0 was recorded examined for association across variables of microvascular health. Two tailed independent samples t-test; one-tailed Pearson correlation; mean±SE; alpha P<0.05.

Results: Twelve patients were recruited to each group (age, years): Fren- 57±3; Fren+ 59±4; one male per group). There were significant differences between groups in valid microvascular density (Fren- 240±23, Fren+ 149±22, p<0.05), total microvascular density (Fren- 328±30; Fren+ 210±29, p<0.05) and MVH score (Fren- 1.01±0.14; Fren+ 0.57±0.12, p<0.05). There were no differences in RBC filling, PBR, or Dval/Dtot (all p>0.05). GIT 2.0 score was negatively associated with valid microvascular density (r=-0.39, p<0.05), RBC filling (r=-0.39, p<0.05), and MVH score (r=-0.44, p<0.05). There was a trend for a negative association with total microvascular density (r=-0.34, p=0.08), PBR (r=-0.29, p=0.11), and Dval/Dtot (r=-0.26, p=0.14).

Conclusion: This feasibility study confirms that the sublingual frenulum may be indicative of perfusion abnormalities in SSc. Moreover, GIT heath scores were inversely associated with variables of microvascular health. The functional significance and pathogenesis of this abnormality warrants further study.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/assessment-of-sublingual-frenulum-perfusion-in-systemic-sclerosis/