How do symptoms of celiac disease differ from age of onset?

Varied. The symptoms of celiac disease are quite varied. However, failure to thrive (failure to gain weight) is a common symptom in child who are diagnoses with celiac disease. Other symptoms of and pain, diarrhea and nutrient deficiencies can be seen in different age groups.
Variable. This is difficult to fully answer since everybody experiences variable symptoms with celiac disease. Best is to ask your gastroenterologist about these age-related manifestations.