Type I Interferonopathies in the Differential Diagnosis of Vasculitis: A Comprehensive Review.

Type I interferonopathies are a heterogeneous group of monogenic autoinflammatory disorders characterized by dysregulated type I interferon (IFN-I) signaling due to pathogenic variants that affect nucleic acid sensing, processing, or downstream signaling pathways. Mutations in genes including TREX1, RNASEH2A/B/C, SAMHD1, ADAR1, STING1 (TMEM173), PSMB8, COPA, and DNASE1L3 lead to persistent activation of innate immune pathways, particularly the cGAS-STING, MDA5, and Toll-like receptor pathways, with subsequent JAK-STAT signaling and sustained overexpression of interferon-stimulated genes. Chronic IFN-I activation promotes endothelial dysfunction, vascular inflammation, and tissue injury, providing a mechanistic link between interferonopathies and vasculitic disorders. Clinically, these conditions present with diverse manifestations, including chilblains, livedo reticularis, necrotizing cutaneous vasculopathy, panniculitis, interstitial lung disease, cerebral vasculopathy, and glomerulonephritis, often resembling autoimmune diseases such as primary central nervous system vasculitis, systemic lupus erythematosus (SLE), poliarteritis nodosa (PAN), immune complex vasculitis, and ANCA-associated vasculitis (AAV). A persistently elevated interferon gene signature represents a valuable diagnostic biomarker that distinguishes these disorders from most classical autoimmune vasculitides and facilitates early recognition. Timely genetic testing is essential to establish an accurate diagnosis, guide patient management, and avoid treatment delays. The present review summarizes the molecular mechanisms linking IFN-I dysregulation to endothelial injury and vasculitis, discusses the clinical spectrum and diagnostic challenges of monogenic interferonopathies, and highlights emerging targeted therapies, particularly Janus kinase inhibitors, that support precision medicine approaches for interferon-driven inflammatory diseases.