Antineutrophil Cytoplasmic Antibody-Associated Vasculitides in Systemic Sclerosis: A Unique Clinical Overlap With Significant Implications for Treatment and Outcomes.

OBJECTIVE

Systemic sclerosis (SSc) is an autoimmune disease characterized by autoantibody production, fibrosis, and vasculopathy. The coexistence of antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV) in SSc is rare and poorly characterized, with limited data on the impact of treatments, particularly high-dose glucocorticoids (GCs), on both conditions. This study aimed to describe the clinical phenotype, management, and outcomes of patients with overlapping SSc and AAV.

METHODS

We conducted a multicenter retrospective study in 18 French centers, including patients who met the 2013 American College of Rheumatology (ACR)/EULAR criteria for SSc and the 2022 ACR/EULAR criteria for AAV. Clinical, biologic, and radiologic data were collected.

RESULTS

We included 30 patients (median age 51.5 years, 83% female). SSc preceded AAV in all cases; 27% had diffuse cutaneous SSc, whereas 73% had limited cutaneous SSc. Anti-Scl70 antibodies were detected in 50%, and interstitial lung disease (ILD) was present in 80%, predominantly with a fibrosing nonspecific interstitial pneumonia pattern (54%). AAV was microscopic polyangiitis in 90%, with myeloperoxidase (MPO)-ANCA positivity in 93%. Renal involvement was common (76%), with a median serum creatinine level of 170 μmol/L (interquartile range [IQR] 120-361 μmol/L) and proteinuria (urine protein to creatinine ratio of 2 g/g creatinine [IQR 0.9-2.3 g/g creatinine]). All patients received GCs in combination with cyclophosphamide (50%) or rituximab (47%). No cases of scleroderma renal crisis were observed. SSc manifestations, including ILD and skin involvement, remained stable during follow-up.

CONCLUSION

AAV, predominantly microscopic polyangiitis with MPO-ANCA, can occur in SSc, particularly in patients with fibrosing ILD and anti-Scl70. Standard vasculitis treatments appear to be effective and do not worsen outcomes in SSc.