Hello @rjm and welcome to Mayo Clinic Connect. I am glad that you found this patient support forum. As you probably know, Connect, is made up of patients and we are not medical professionals. We do, however, have other members who have discussed this disorder and I hope that some of them will respond to your questions.

I applaud you for wanting to have as much information as you can. As you probably know Collagenous Gastritis is a rare disorder, which probably explains the difficulty in getting a diagnosis for your daughter's health problems. I am glad to hear that her blood work is showing improvement.

To help you in your search for more information, here is a link to a Mayo Clinic video talking more about this rare condition. Just click on this link, https://www.youtube.com/watch?v=XY-0Fsv20sw.

Here is some information from the National Institute of Health website that might be helpful as well, https://rarediseases.info.nih.gov/diseases/10961/collagenous-gastritis/

From what you say your main concern right now is your daughter's energy level and stamina. Is that correct?