What Causes Fever And Loss Of Weight In A Teenager?

16 ur old daughter suddenly became really sick, low grade fever, very confused and not making sense. Very tired but unable to sleep. Became worried and scared but cant say about what. Within two days she looks like she has lost 15 lbs and is really pale and very thin. She looks aweful. This has happened three times in the last 4 years. Last time she ended up in acoma at Mayo Hospital with no diagnosis after 38 days inpatient. It started again two days ago and I feel helpless as a mom cause no one can tell me what is wrong. Please help.