Five days of fever and myocardial inflammation.

Multisystem inflammatory syndrome in children is an emerging pediatric illness associated with severe acute respiratory syndrome coronavirus 2 infection. The syndrome is rare, and evidence-based guidelines are lacking. This report reviews a patient who presented for medical care multiple times early in the course of his illness, thus offering near-daily documentation of symptoms and laboratory abnormalities. The patient did not have thrombocytopenia, anemia, or myocardial inflammation until the fifth day of fever. These laboratory abnormalities coincided with the onset of rash, conjunctival injection, vomiting, and diarrhea: clinical signs that could serve as indicators for when to obtain blood tests. The timing of this patient's onset of multisystem involvement suggests that testing for multisystem inflammatory syndrome in children after only 24 h of fever, as the Centers for Disease Control and Prevention recommends, may yield false-negative results. Testing for multisystem inflammatory syndrome in children after 4 days of fever may be more reliable.