And, found out too late that my mother did not have auto-immune disease. She had chronic lyme disease and interstitial cystitis which is a systematic disease-infection, not just related to the bladder, and it does cause psoriasis. Neither one of which, lyme or IC, is routinely tested for and many medical professionals don't even know about it or how to test for it.
There are many types of skin disorders from an array of sources, and I am not claiming that they are all casued by lyme and or IC...some specaiists claim they are one in the same or coinfections. Lupus also causes a rash...that is also suspected to be lyme disease. The skin is a reflection of what is happening inside the body.
Many people would just like to believe in "auto-immune"...a whacky immune system, rather than question what wans't tested for and find out the truth.