Is it possible to have hand, foot, and mouth with NO rash/blisters?

My daughter's daycare sent out an email on Friday to let us know that they'd had a few cases of HFM confirmed that day. She was at the daycare Tuesday-Thursday and came down with a low fever Friday morning, which then shot up to 40 on Saturday and has mostly stayed high since then. As soon as I saw their email, I suspected HFM because the timing fits for the incubation period, but the catch is that she does NOT have any rash/blisters anywhere and it's been over 3 days now since she first got sick.

We did take her to the doctor to check for the possibility of an unrelated bacterial infection, but that has been ruled out. Other than a high fever and swollen/painful lymph nodes, she doesn't seem to have any other symptoms of anything.