A 12-year-old girl is brought to the clinic by her parents with a 3-week history of worsening fatigue, easy bruising, and recurrent nosebleeds. She states, “I feel too tired to play with my friends, and my legs are covered in tiny red spots.” Her parents report that she has not had any recent viral illnesses and takes no medications. Her past medical history is unremarkable.

She appears pale and fatigued. She is afebrile. Her blood pressure is 100/60 mmHg with a heart rate of 105 bpm. She appears pale and fatigued; there is no jaundice.