I have coeliac disease (gluten intolerance) and a host of other, as yet undiagnosed, problems including a malar rash and enough other stuff to have had Lupus considered as a diagnosis. Coeliac disease is another autoimmune disorder and it occurs in people who have the same genetic background as rheumatoid arthritis, lupus, some thyroid disorders, etc. It seems to mean that if you have a family history of any of these things, then you have the genetic susceptibility that may mean you have more chance to get any one of the others on the list. It does also seem that rather more people than just by chance end up with more than one of these autoimmune disorders.
Having gone for probably 20 years myself with what should have been obvious symptoms of coeliac disease and the malabsorption problems that go with untreated coeliac disease (including anaemia, folate and B12 deficiencies with no obvious cause) I'd now strongly suggest that you do everything you can to get yourself screened for it. It is a very common problem (1 in 100 people have coeliac disease) but one that is not diagnosed anywhere near often enough (probably less than 1 in 2000 people actually get diagnosed), and GPs and specialists alike seem to have very little understanding. Check out the coeliacuk dot org dot uk website for a bit more info, and then see if you can convince your GP to do the blood screening tests as a first step. In the meantime, DON'T change your diet - you actually have to be eating a full gluten containing diet in order for any of the tests to be positive. This is one case where antibodies do return to normal when treated by the gluten free diet.