Causes of Scleroderma
Scleroderma (systemic sclerosis) is an autoimmune connective tissue disease of unknown cause that develops through a complex interplay of genetic predisposition, environmental triggers, immune dysregulation, vascular injury, and progressive fibrosis. 1
Pathogenic Mechanisms
The disease pathogenesis involves three core pathological processes that work in sequence and synergistically 2, 1:
1. Vascular Injury (Initial Trigger)
- Endothelial cell damage occurs early, triggered by autoimmune responses against a backdrop of genetic susceptibility
- This vascular injury impairs angiogenesis and vasculogenesis, leading to capillary loss and arteriolar constriction
- The damaged endothelium may be infected by bacteria or viruses, potentially playing a role in inducing vasculitis 3
2. Immune Dysregulation and Inflammation
- Altered balance of acquired and innate immune systems leads to release of cytokines (particularly TGF-β), chemokines, and autoantibodies 4
- Immune cell infiltration occurs in affected tissues, with sustained inflammation
- M1 macrophages predominate in early inflammatory stages, while M2 macrophages characterize the fibrotic stage 5
3. Progressive Fibrosis
- Chronic inflammation drives persistent fibroblast activation
- TGF-β signaling in fibroblasts promotes myofibroblast differentiation
- Excessive extracellular matrix deposition and collagen accumulation result in tissue fibrosis affecting skin and internal organs 4
Proposed Triggering Factors
While no definitive cause has been established, several factors have been implicated 6, 3:
Infectious Agents
- Parvovirus B19
- Cytomegalovirus
- Epstein-Barr virus
- Retroviruses
Molecular mimicry between viral proteins and autoantibody targets may initiate antibody responses, though direct causal association remains unproven 3
Genetic and Epigenetic Factors
- Permissive genetic background predisposes to disease development
- Specific HLA associations noted in some studies 1, 6
Environmental Factors
- Work synergistically with genetic predisposition
- Specific environmental triggers not definitively identified 1
Important Clinical Context
The disease is NOT caused by a single identifiable factor but rather represents a final common pathway where multiple predisposing elements converge. The exact sequence of events—whether vascular injury precedes immune activation or vice versa—remains debated, but current evidence suggests vascular endothelial damage is the initiating event 1.
Key Distinguishing Features
- SSc differs from localized scleroderma, which does NOT involve internal organs or progress to systemic disease 7
- Scleroderma-like syndromes can be caused by specific identifiable factors (drugs, toxins, metabolic disorders, malignancy) and must be distinguished from true systemic sclerosis 8
Clinical Implications
Understanding that SSc results from autoimmune-triggered vascular injury followed by inflammation and fibrosis explains why: