Once you have one autoimmune disease, it's not that uncommon to collect more. I understand celiac disease often accompanies other AI diseases; many people who have AI disease have at least an intolerance to wheat, if not outright celiac disease. The bright side of your situation is that celiac can be controlled with diet alone. No drugs! And if the celiac is responsible for your cd symptoms, then perhaps you can stop taking the cd drugs as well. Not that it's easy to eat gluten free (it's not), but it sure beats adding another drug to the medicine chest.
Current dx: Rheumatoid Arthritis
Suspected dx: UCTD/Early Lupus
Current Meds: Enbrel, Plaquenil, Aciphex, Ultracet, Zyrtec, Allavert-D, Zantac, Tylenol PM
Past Meds: Relafen, Vioxx, Mobic, Voltaren, Sulfasalazine, Entocort, Prednisone, Humira, Reglan