what can cause a hard enlarged lymph node and a swollen thyroid in a child

Have you tested for a thyroid disorder? Hyper or hypo? I have a son diagnosed with celiac. We saw a celiac specialist and she said that the first thing she always checks for is thyroid issues. It could be related to a food allergy/autoimmune response by the body. Our celiac doctor said that she diagnosed her own daughter with hashimotos. Ask your pediatrician if you can get a thyroid screen to see what your daughter's levels are. Best of luck with your daughter.

The symptoms that you describe are most often due to a benign condition called thyroiditis. It may be useful to treat this with a course of antibiotics to see if the symptoms improve. Of course, there may be other, more dangerous conditions causing these symptoms so the best course of action to pursue is to take your child to the pediatrician. They can start treatment and decide if she needs to see an ENT specialist who treats thyroid disorders.