Gray-Violet Plaque in an Immunocompromised Girl

A 4-year-old girl with newly diagnosed acute lymphocytic leukemia, currently on her initial course of chemotherapy with vincristine, daunorubicin, and methotrexate developed a painful lesion on her left triceps; the tender area was beneath an adhesive bandage placed where she had received DTaP (diphtheria-tetanus-pertussis) and polio vaccinations 3 weeks earlier. What is your diagnosis?
Source: JAMA Dermatology - Category: Dermatology Source Type: research