According to my husband, David Sulman, a gastroenterologist:
With celiac sprue, symptoms (diarrhea, malabsorption) don't appear until
wheat, rye and/or barley have been introduced into the diet.  If the child
follows a strict gluten-free diet, these symptoms disappear and he/she
develops normally and can live a normal life.  Many children lose the
symptoms and can eat normally again at a certain, unpredictable age.  Some
of these people, decades later, again develop diarrhea and malabsorption
and need to resume the very restrictive diet.  There is a celiac support
group, and the doctor should put the family in touch with it for help with
the diet and other aspects.  (We don't have the address at home, but could
post it later if needed).  Celiac disease really can only be definitively
diagnosed with a small bowel biopsy.  It is often misdiagnosed, as a cause
for chronic diarrhea.  We do not know how breastfeeding fits in, but
perhaps others on Lactnet can add in here.

David Sulman, MD and Anne Altshuler, RN, MS, IBCLC and LLL leader in Madison, WI