Hello Patty and welcome to Mayo Connect! I’m sorry to hear what is happening to you and I personal know how frustrating it is to deal with autoimmune conditions. I am currently in the process of being diagnosed with Lupus and I meet 6 of the 11 criteria for diagnosis, which you only need 4. It’s great you are already seeing a rheumatologist, they are the best people for autoimmune conditions. Has yours run any other bloodwork and have they considered any other medication treatments? Also, has there been any imaging done for the chest pain? That symptom alone can mean a lot of things but with lupus it can be inflammation around the lining or the heart of lungs that causes it.
Now, anti-seizure medications is on the list for DIL, however, I’d speak with your doctor before you cut the medication (which usually has to be tapered off for most people) to see if it the medication or you have to consider other conditions rather than DIL. I saw Lupus, Psoriatic Arthritis and Reactive Arthritis are options on the table but has RA been considered since from what is stated above you do have that in your family history? Also, since your symptoms are improving on Methotrexate that is good, it can take a while but that is one medication that is used in Lupus as well as many other autoimmune conditions, stopping it could bring back your symptoms especially since you don’t know for sure which condition this is. My best suggestion is look at all conditions that your MD has suggested and do as much research. Then make an appointment to speak with him/her to bring up further questions or concerns.
Now if this is true DIL then it could take, like you said, months before you notice a true improvement. Your doctor took you off the original medication, the reason they may not have taken you off the gabapentin is to figure out what medication it is causing DIL that way it can be documented and no health care provider in the future will attempt to put you on it again. Again, I’m so sorry you are going through this as any form of lupus can be frustrating to deal with but hang in there and good luck.

I hope this helped!

Marilyssa Trujillo