From Kawasaki disease to MIS-C: The Bergamo experience

Kawasaki disease (KD), although rare (affects about 15 children out of 100,000/year) and self-limiting, it is the second most frequent cause of pediatric acquired heart disease in Western countries. The classic KD is diagnosed by fever and at least 4 clinical signs between conjunctivitis, mucositis, polymorphic rash, erythema and edema of hands and feet or lymphadenopathy; if clinical signs are less than 4 the incomplete KD can be diagnosed together with specific laboratory criteria. Since March 2020, at the time of the greatest spread of the SARS-CoV-2 epidemic in our province, we found over 20 children, admitted to the Pediatrics of our hospital, with clinical pictures very similar to Kawasaki disease. In addition to signs of mucocutaneous inflammation, some children had a significant systemic inflammation with severe heart involvement, up to shock in some cases. In the next months, similar cases were reported in areas of the world with a high spread of the virus, and the scientific community coined the name of Multisystem Inflammatory Syndrome in Children (MIS-C) for this form linked to SARS-CoV-2. KD conventional therapy based on intravenous immunoglobulin, acetylsalicylic acid and systemic steroids resolved the inflammation in all children. This article critically discusses the common characteristics of the two diseases and hypothesizes that they belong to the same pathological condition with a wide spectrum of clinical manifestations; it proposes the diagnostic framework for this new inflammatory condition based on clinical and laboratory characteristics and, finally, outlines the principles of treatment.