The silicone breast implant was once thought to cause Lupus, arthritis and other collagen vascular disorders. It was taken off the US market from 1992 to 2006. Research then showed that there was no relationship between silicone exposure and Lupus, arthritis and other collagen vascular disorders. In Europe and in Canada the silicone implant was never taken off the market.
That being said, there a still many who believe that silicone caused their illnesses and that it should never be used.
For someone like you, who has a high risk for immune system disorders I would recommend the saline implant. It's a great implant. It gives you the same shape, size and look that a silicone implant would give and only gives up a little in feel. Now with the submuscular placement of breast implants, this feel difference can be very minimal.