This child has Idiopathic Thrombocytopenic Purpura (ITP).
The child is well and has evidence on exam of both petechiae and purpura. There are no concerning features such as adenopathy, hepatosplenomegaly or joint bleeding. There are normal lab values except for the low platelet count.
Consolini DM. Thrombocytopenia in infants and children. Pediatrics in Review 2011; 32: 135-49.
Review of platelet disorders, causes of thrombocytopenia in children with a focus on ITP- good tables and diagrams for learning.