Hi Jacksmom,
Yes, those are stretch marks from the pred and as Crohn's Mom said they won't go away. The color will fade with time. My son has a number of stretch marks from being on prednisone but his are on his belly so they are easy to hide.
As for the growth.
He is very unlikely to grow as long as he is on steroids of any kind - prednisone or entocort.
He is also very unlikely to grow until he gets into at least partial remission.
I don't know what other treatment he's getting beside the pred so I can't comment on his treatment and potential remission.
It's good that he's gained weight but at least some of it may be due to the prednisone causing water retention and it will go away again once he's off the pred.
I suggest, if you aren't already doing so, that you see if he will add some liquid nutritional sources to his diet. Ideally he would go to those exclusively - no regular food at all. This would almost certainly end any symptoms he has within 2 or 3 weeks and put him into real remission if he did it for 6 to 8 weeks.
Assuming (since he's 12) that he won't go for this plan, perhaps you could persuade him to do it just on weekends - to give his gut a break and help it heal faster. It will also help him grow taller faster.
But just adding some liquid nutrition like Boost or Ensure will help get him solid easily digested nutrition every day.
Once he's off steroids and gets into remission he should start growing. Some kids get "catch up" growth where they grow a lot quickly until they are back on the curve close to where they should be. Other kids don't - they just poke along on their new curve. And then there are all the ones in between.
The bottom line is that growth is tied to remission. If he's not growing (assuming no steroids) then he's not in remission. Not growing means that he's had less than 1/2" growth over a period of 9 months or zero growth in 6 months or less than 1" in a year and a half. It's hard to give definite figures like this because a lot of it is about looking at the pattern or lack of pattern over a long period of time. Ideally two years or more is the appropriate time period for evaluating growth issues. But these are the numbers that seemed appropriate when we were dealing with growth issues.
Keep in mind that kids are like plants - they grow in the spring and summer. Average growth per year is 2" except during adolescent growth spurt when it's more like 4".
So don't freak out if he doesn't grow 4 inches by Valentines Day.
Give him til Labor Day OK?