Has Anyone Heard Of Herpangina?

My 3rd son is 18months. He was diagnosed with herpangina today at his paediatrician. It is something like hfmd but only in the mouth area. Nothing is visible on his mouth, hands and feet. He doesn't have fever and he still play with his siblings but he refused to eat or drink and kept fussing when it's time to sleep. Now it's confirmed my eldest and 2nd child have it too. You have to quarantine them for 2 weeks. Please know its symptoms. Be aware.