A 23-month-old child presented with fever and lethargy. Two days earlier, her parents noticed she was warm on waking, and her temperature was recorded as 101.6°F (38.7°C). She was given acetaminophen and ibuprofen and slept more than usual that day. Her evening temperature was 103.7°F (39.8°C). The patient had been exposed to a child with streptococcal throat infection at day care earlier in the week.

At the time of presentation the patient was drinking well but pickier than usual with food. She had no significant medical history and was current on immunizations, including those for COVID-19. She was irritable, but there were no abnormal findings on physical examination. Laboratory testing was negative for COVID-19, influenza, and group A streptococci. Over the next few days, her activity level returned to normal; however, low-grade fevers between 100.4°F and 101.3°F (38°C and 38.5°C) persisted.

Four days after her first fever, she developed a rash that began on her lower back, then spread to her arms, legs, and cheeks (Figure 1 and Figure 2). The rash was erythematous, blanching, and macular.