Lupus erythematosus: The cause of lupus erythematosus is not known. Viruses, ultraviolet light, and some drugs may trigger the immune system to attack its own tissues. Female hormones may also influence expression of lupus erythematosis. Recently, research has led scientists to suspect that a mutation in a gene responsible for disposal of dying cells may be involved in triggering the disease.

Rheumatoid arthritis: In rheumatoid arthritis, white blood cells (the cells that normally attack unwanted invaders) are mobilized to attack its own tissues. Specifically, they move from the blood into the membranes that surround the joints (synovium). The resulting inflammation prompts the release of substances that eventually cause the synovium to thicken. Over months or years, the gradual thickening distorts the affected joint, misaligns it, and eventually destroys it. The surrounding cartilage, bone, tendons and ligaments may also be damaged. The trigger for this process is unknown. It is believed that many factors play a role, including genetics, health habits (e.g., smoking), and exposure to viruses.

Scleroderma: Scleroderma results from overproduction and accumulation of collagen, a fibrous protein that makes up the connective tissues in the body. Accumulation of collagen in the skin results in the thick, hard layers characteristic of scleroderma. In systemic scleroderma, this process also affects other organs in the body. The trigger for abnormal collagen production remains unclear but researchers believe the immune system plays a key role.  

Dermatomyositis: The cause of dermatomyositis is unknown. However, researchers suspect that it is an autoimmune disorder. Genetics may also play a role. The patient’s immune system is triggered to attack the blood vessels supplying oxygen to muscle and skin. The exact triggers have not been identified, but some researchers believe that exposure to certain drugs or viruses may play a role.