Crusted lesions on the face

A 4 year old presents with crusted lesions on the face that have developed over the past 2 days. They started as small vesicles on a small erythematous macular area and then started to spread. Considering the potential infectious agents, discuss possible differential diagnoses and their pathophysiology.

Discuss three differential diagnoses in young children that may present as crusted lesions
Describe the pathophysiology associated with each of these three differential diagnoses