Occupational and Environmental Causes of Autoimmune Diseases

Systemic autoimmune diseases (AID) regroup a broad range of related diseases characterized by self-damaging immune responses. They mainly comprise systemic lupus, systemic sclerosis and rheumatoid arthritis and remain a significant clinical challenge. Rheumatoid arthritis (RA) is a degenerative disease associated with chronic inflammation that ultimately leads to joint damage, deformation and destruction. Systemic lupus erythematosus (SLE) is characterized by tissue injury resulting from immune responses and serological changes. This multifaceted etiology AID is initiated by the loss of tolerance to self-antigens and the accumulation of autoreactive B and T cells that promote autoreactive antibody production, immune complex formation and activated mononuclear cell infiltration in affected tissues. Finally, small vessels-vasculopathology, internal tissue fibrogenesis and thickening skin characterize systematic sclerosis (SSc) patients. These lesions derive from dysregulated immune functions altering connective tissue integrity.

Several risk factors have been pinpointed to explain the triggering of these AID. Scientists have managed to identify the main genetic factors. Susceptibility to AID is strongly associated to MHC class II polymorphisms and adaptive immunity activation (particularly effector T lymphocytes).

Nevertheless, several studies have also emphasized the contribution of environmental factors, which may function as triggers of innate immunity and may contribute to the breakdown of self-tolerance by modifying protein antigens. Cigarette smoking has proven to be a strong risk factor for seropositive RA and SLE. Cigarette smoke leads to post-translational modifications of antigens by citrullination (citrullinated antigens) that induce the production of anticitrullinated protein antibodies (ACPA) and the onset of ACPA-positive RA. Occupational factors may also cause or trigger AID. In a retrospective study conjointly performed by the Cliniques Universitaires Saint-Luc (CUSL) and UZ Leuven, it was concluded that an estimated 50% of male patients suffering from SSc have occupational exposure to silica and solvents. These findings indicate that environmental factors can provide clinically useful information in the management of AID patients.

Inclusion criteria

• Clinically active lupus; systemic sclerosis; rheumatoid arthritis
• At least 18 years old
• Without first line disease-modifying therapy
• Written informed consent must be obtained before any assessment is performed

Exclusion criteria

• Younger than 18
• Wearers of metal prostheses