Ab1218 Calcinosis in Systemic Sclerosis: Prevalence, Clinical Correlations, and Autoantibody Associations – A Retrospective Cohort Study

Background: Calcinosis, or calcium deposits in skin and soft tissues, is a notable clinical feature of systemic sclerosis (SSc) occurring in around 20% of patients. However, its pathogenesis is unclear and likely involves microvascular injury and dysregulated calcification responses. Calcinosis can lead to painful nodules and ulcers, often on the fingers, and correlates with a history of ischemic digital loss affecting quality of life of patients with SSc. At present, no direct strong association with particular autoantibodies or specific clinical features of the disease has been demonstrated. Objectives: To evaluate prevalence of calcinosis in a Systemic Sclerosis cohort, association with other clinical manifestation and autoantibodies. Methods: A retrospective analysis was conducted on patients that met ACR/EULAR classification criteria for SSc. Clinical characteristics, comorbidities and commonly SSc-associated autoantibodies from these patients were collected. The association between categorical variables was assessed by chi-squared or Fisher exact tests as appropriate; Mann-Whitney test was applied to compare continuous variables between subgroups of patients, as appropriate. Correlation among variables was assessed using Pearson correlation coefficients. Results: The study cohort consisted of 331 SSc patients from our Scleroderma Unit. Of these, 46 (13.8%) presented with at least one calcinosis during the disease course, 27 (58.6%) were classified as limited cutaneous SSc, the other 10 (41,3%) as diffuse cutaneous SSc (dcSSc). Patients with and without calcinosis were compared. Limited cutaneous subtype was equally distributed between the groups. The two groups had comparable median age, age of onset, and female prevalence. Notably, other autoimmune conditions were more common in the calcinosis group (4.3% vs 0.7%, p=0.038). Pitting scars and acral ulcers were also more frequent in patient with calcinosis (54.3% vs 29.8%, p=0.001 and 58.7% vs 33%, pConclusion: The correlations between calcinosis, pitting scars, and acral ulcers highlight the need to better understand the pathophysiological mechanisms linking these manifestations in SSc. One hypothesized mechanism is that vascular injury and ischemia may contribute to dystrophic calcification in affected tissues, as ischemic digital loss is more common in SSc patients with calcinosis. Additionally, the association between calcinosis and osteoporosis suggests a possible connection related to calcium metabolism, though the exact biological mechanisms underlying this relationship remain to be elucidated. Overall, while no strong associations were found between calcinosis and a broader range of clinical features and autoantibodies, this reaffirms the complex, multifactorial nature of calcinosis in SSc. Further research into the pathophysiology, including vascular contributions, is critical to guide targeted treatment development and delineate the clinical implications of this debilitating manifestation for SSc patients. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.