What Are We Missing in Our Search for MIS-C?

Abstract

A previously healthy 3-year-old boy presented with 6 days of fever and fatigue. Three days before, he saw his pediatrician and had negative rapid strep antigen and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction test results. Given persistent fever up to 40°C with decreased appetite and urine output, the patient presented to the emergency department. There was no reported rash, skin peeling, eye redness, redness of the oral mucosa, congestion, rhinorrhea, cough, shortness of breath, chest pain, abdominal pain, nausea, vomiting, or diarrhea. The patient had recently started preschool but had no known exposure to the coronavirus disease 2019 (COVID-19). On arrival, the patient was febrile to 39.2°C, mildly tachycardic, and normotensive. On examination, he had clear conjunctivae, a normal oropharynx, and moist mucous membranes. No rash, extremity swelling, or lymphadenopathy was appreciated. He was breathing comfortably, and his lungs were clear to auscultation bilaterally. His abdomen was soft and nontender with mild left-sided flank tenderness. Given the patient’s prolonged fever, multisystem inflammatory syndrome in children (MIS-C) was considered and an extensive laboratory evaluation was initiated, including all the laboratories suggested as potentially useful in the evaluation of MIS-C (Table 1). Laboratory results were notable for normal white blood cell and platelet counts and a metabolic panel with normal sodium and albumin. Inflammatory markers were elevated with a C-reactive protein (CRP) level of 14 mg/dL, an erythrocyte sedimentation rate (ESR) of 110 mm/hour, and mild elevations of ferritin, D-dimer, and fibrinogen levels. The patient’s troponin level was within normal limits, and his B-type natriuretic peptide (BNP) level was mildly elevated. A urinalysis was notable for small protein, negative nitrite results, small leukocyte esterase, …