Digital vasculopathy in systemic sclerosis (SSc) consists of a spectrum of Raynaud's phenomenon (RP), digital ulcers (DUs), critical digital ischaemia and escalation to gangrene. The complications of severe digital vasculopathy often require hospital-based management with intravenous therapies and surgery.1–3 Although gangrene is not infrequent in the clinic, data on the prevalence and implications of gangrene in patients with SSc are scarce.3–7 The DU Outcomes (DUO) Registry is a European, prospective, multicentre, observational cohort of patients with SSc and past and/or current DUs at enrolment.8–10 The aims of the current study were (i) to describe the characteristics of an SSc–DU population according to the presence/history of gangrene and (ii) to identify the risk factors for the development of incident gangrene.

All patients in the participating centres with SSc and a history or presence of DUs are eligible for inclusion in the DUO Registry, irrespective of their treatment regimen. At enrolment, data were collected on demographic and clinical variables. Patients were categorised into three groups according to their past history of gangrene and current gangrene status at enrolment: ‘never gangrene’: no past and no current gangrene; ‘ever gangrene’: past and/or current gangrene; and ‘current gangrene’: gangrene reported at enrolment, irrespective of gangrene history (a subset of the ‘ever gangrene’ group).

Categorical variables were analysed using descriptive statistics. Potential risk factors for the development of incident gangrene in patients with ≥1 follow-up visit and no current gangrene at enrolment were analysed using univariable logistic regression (ULR) conducted on demographics, clinical variables and autoantibody measurements collected at enrolment. Multivariable logistic regression (MLR) using forward selection was conducted on patients with complete covariate information using those variables with a p value <0.15 and sample size >3000 from the ULR models, considering interdependency among similar factors.

Among the 4944 patients enrolled in the DUO Registry from April 2008 to November 2014, 4642 had information recorded on their gangrene status: 81.6% (n=3787) were categorised as ‘never gangrene’, 18.4% (n=855) as ‘ever gangrene’ and 5.6% (n=258) as ‘current gangrene’. The three groups were generally similar regarding demographics and SSc characteristics, although more current smokers at enrolment were in the ‘ever gangrene’ and ‘current gangrene’ groups than in the ‘never gangrene’ group, and the ‘current gangrene’ group had the shortest time between first RP and enrolment (table 1). The proportion of patients with a history of DU-associated complications, interventions and hospitalisations was greater in the ‘ever gangrene’ group compared with the ‘never gangrene’ group.

Overall, 3809 patients were eligible for inclusion in the ULR analysis; the final number of patients included in each ULR model varied depending on missing data (table 2A). On MLR analysis, being a current/former smoker, having ≥3 finger DUs, previous gangrene and previous upper limb sympathectomy were independent risk factors at enrolment for development of incident gangrene (table 2B).

This analysis was the largest to date describing an SSc–DU population according to the presence/history of gangrene at enrolment and risk factors for incident gangrene during follow-up. It has demonstrated that, in current practice, gangrene is still a common event occurring in 18% of patients with SSc–DUs. Participating centres involved in the DUO Registry are specialist centres for the management of SSc–DUs; this may be selective for patients with more severe vascular disease, and therefore more prevalent gangrene. Multivariate analyses indicated that, in patients with no current gangrene, along with previous gangrene, being a current/former smoker, having ≥3 DUs and previous upper limb sympathectomy were independent risk factors at enrolment for developing incident gangrene. These results will help to risk-stratify patients with SSc–DUs and to evaluate preventive gangrene management strategies.