A previously healthy eight year old boy presented to the emergency depament with high grade fever, ahralgia, pruiritic erythematous rash and lymphadenopathy. He had completed 8 days out of a 10 day course of cefaclor for an upper respiratory tract infection. Which of the following possibilities should be initially suspected?

Boy in the questions who developed the fever, rash, lymphadenopathy, after taking cefaclor for UI is suffering from drug induced serum sickness. It's a type 3 hypersensitivity mediated by IgG antibody. Ref: Essentials of emergency medicine By Richard Aghababian page307; What to do About Allergies By Harvard Health Publications page 8.