I've had hemorrhoids since I was about 14 or 15, then had surgery on them when I was 20. The surgery went horribly! It was an excruciating recovery, and I don't recommend it at all! They did not know that I had Crohn's when they did the surgery. Because I healed so poorly from the surgery they investigated further and (after a colonoscopy, bloods and more tests) found that I have Crohn's and that was why the hemorrhoids were there and why they were not healing properly after the surgery. Once I started to get the Crohn's more under control the hemorrhoids got smaller and stopped bothering me. I still have them, but they are smaller (size of a pea/small lima bean, to give some perspective- when they were really bad they were the size of a quarter or more
) and they don't really cause any pain or discomfort.
They are definitely part of the Crohn's, which can cause inflammation on any part of the digestive tract. And Crohn's can cause circulation issues like varicose veins and hemorrhoids.
I wouldn't worry about them too much unless they are very painful or start to bleed a lot. Definitely tell the doctor, because you never know. It looks like your son hasn't been on Humira for very long, so maybe as that starts to work it will take care of them? Also I saw that he had been on Pentasa, but that it failed. I started on Pentasa, and it was I think the main thing that helped clear up the hemorrhoid problem, but it did not solve the other inflammation and symptoms. When I have gone off of Pentasa, even for a few days, I can feel the hemorrhoids get worse. So I think that the Pentasa really helps with the inflammation in that area..at least that's been my experience with it.
Sorry to be so wordy! Hope it was helpful