A Young Girl With Recurring Alopecia

A 4-year-old girl is seen for progressively worsening alopecia. Her past medical history is significant for complete hair loss, including eyelashes and eyebrows, 2 years ago. The hair grew back but has begun falling out again, with spots of hair loss visible. She has no known allergies and is otherwise well. Results of physical examination are: height, 36 in; weight, 27 lb; temperature, 36.2°C (97.1°F); heart rate, 90 beats/min; respiratory rate, 23 breaths/min; SpO₂: 100% on room air.