Concerned toddler mom

Thank you for your prompt reply! I will certainly follow up with that elevated Iga, his TSH has been on the high end of normal as well. Thank you for the advice. I sincerely appreciate it. So tired of hearing from relatives "maybe he' just small" when he was a little chunker until 1, when all the problems began.

My 2.5 year old has had weight issues since the age of 1. He has gained very little weight since then and has completely fallen off his growth curve and had been diagnosed with failure to thrive. His pediatrician has been concerned enough to put him through a full cardiac workup and has completed lab work multiple times. My son has chronic diarrhea...