Entero-Arthritis, Crohns & 6-MP. Please Help!

Hello, I'm Stacy (new to this site) and I was diagnosed with Crohn's and Auto-Immune Hepatitis in 2014. Two years later I was diagnosed with Entero-arthritis, which, as I understand it, is a type of arthritis that many Crohn's patients develop. I suffer from moderate to severe pain and swelling in the small joints (ankles, knees, wrists, fingers) as well as sacroiliac. Currently, I'm on Stelara for the Crohn's and it has me more or less in remission. The arthritis is another matter entirely. I continue to have swollen and painful joints, and the pain affects my activities of daily living. After a dozen different drugs have failed to help the pain & swelling, the rheumatologist put me on 6-mercaptopurine and I started today. The dosage regimen is one 50 mg tablet once per day, with goal to increase to 75 mg once per day.

But, here's my confusion and my question- I thought 6-MP is given for the indication of IBD. I don't see anything in the literature about maintaining a patient on a biologic (Stelara) and giving 6-mercaptopurine concomitantly for entero-arthritis. Please, have any of you had this experience or maybe know of it? It's not that I'm doubting the qualifications of my specialist, it's just that I don't see anyone else online or in the clinical literature who is taking 6-MP for entero-arthritis. I was hoping to see someone's testimonial online that says, "Yes, I am taking 6-MP and my arthritis pain is gone!", lol.

I thought I would come here and hopefully get alot of information from real people who have situation/experience similar to mine.

Thanking you all in advance.
Stacy