Associations with digital ulcers in a large cohort of systemic sclerosis: results from the Canadian Scleroderma Research Group registry

Objective: Digital ulcers are a common complication of systemic sclerosis (SSc; scleroderma). Approximately half of SSc patients have had a digital ulcer, but information is lacking on whether digital ulcers are associated with patient demographics and clinical outcomes. We wanted to determine the associations between digital ulcers and other SSc vascular complications and organ involvement.

Methods: Data from the Canadian Scleroderma Research Group are collected annually on SSc patients, including presence, location, and number of digital ulcers; complications from digital ulcers; internal organ involvement; skin score; and laboratory results. Correlation coefficients, chi-square test, and logistic regression modeling were done to determine the associations of digital ulcers with other factors, including internal organ complications.

Results: A total of 938 patients were included; 86% were women, the mean age was 55 years, the mean disease duration was 13.6 years, and 50% had limited cutaneous SSc. Eight percent had a digital ulcer currently and 44% had a digital ulcer ever; 53.1% had digital pitting scars. Digital ulcers were associated with increased modified Rodnan skin score (P = 0.0001), hand and finger skin score (P = 0.0001), Health Assessment Questionnaire score (P = 0.0001) and disease duration (P = 0.001), younger age of SSc onset (P = 0.0001), interstitial lung disease (ILD; P = 0.0001), and topoisomerase I (Scl-70) antibodies (P = 0.0001) in limited and diffuse cutaneous SSc subsets. Digital ulcers were not associated with sex (P = 0.95), smoking (P = 0.9), pulmonary arterial hypertension (PAH; P = 0.35), and scleroderma renal crisis (SRC; P = 0.569). Digital ulcers were further associated with reduced diffusing capacity for carbon monoxide (DLCO; P = 0.0001) and esophageal involvement (P = 0.0001) in diffuse cutaneous SSc only.

Conclusion: Digital ulcers are associated with worse disease, including skin and lung involvement, but are not associated with PAH and SRC. However, the low DLCO that is associated with SRC could represent ILD or microvasculopathy.