What Causes Pain In Throat With Difficulty In Swallowing?

Hi my nephew has been admitted to the hospitals showing signs of pale skin, fatigue and constant fever around 39.5 deg. He now has problems with his throat and is having problems swalling food. Doctors think it may be anemia with low red blood cells. Are this the signs of anemia? He is around 14 yrs and around 45-50 kg.