Silicon and silicone: theoretical and clinical implications of breast implants

In the past 10 years, there have been multiple published reports associating silicone breast implants with scleroderma, morphea, SLE, rheumatoid arthritis, CREST syndrome and "human adjuvant disease." The alleged offending material, silicone, is a synthetic polymer containing a silicon-oxygen backbone. Beginning with the heating of SiO2 in the presence of carbon, elemental silicon is produced. Methylchloride is added and the resulting product is hydrolyzed to form low molecular weight prepolymers which are linked to form linear silicone polymers and cross-linked to yield silicone rubbers or elastomers. The polymeric and hydrophobic characteristics of silicone and the presence of electrostatic charges and organic sidegroups make silicone a potentially ideal immunogen, leading to cross-reactivity with autoantigens. Silicon is an essential constituent of proteoglycans which theoretically could result in immunological cross-reactions between silicone and connective tissues. Although the literature contains numerous examples of silicone-associated autoimmune disease, there is no consistent pattern of immunological abnormalities observed. There are, however, some intriguing and interesting observations. Further large-scale studies are needed to determine if a link between silicone exposure and autoimmunity exists. Also, since the inducing events of autoimmune diseases are unknown, studies on silicone could provide a model for autoimmune diseases associated with toxicological factors.