Barbara Kienzle, BSN, RN

Kawasaki Disease (KD), a vasculitis of unknown origin affecting young children, has certainly taken center stage during the COVID-19 pandemic. This newfound awareness of KD stems from the emergence of Multisystem Inflammatory Syndrome in Children (MIS-C), an inflammatory condition with similar symptoms as KD occurring 2 to 6 weeks following a SARS-CoV-2 infection.

Burney and colleagues present a fascinating exploration of the social, environmental, economic and geographical factors that may have contributed to the decrease in KD in the United States during the height of the COVID-19 pandemic. Along with the typical patient demographic information, the authors collected statistics using GPS to identify neighborhoods with an incidence of KD, reviewed mobile phone data to indicate time spent away from home, measured nitrogen dioxide levels as an index of pollution and identified circulating viral levels. Gathering and analyzing all of this data was quite a collaborative effort.

The wealth of information compiled indicates an association between school closures, masking policies, a decrease in pollution and circulating viruses, resulting in a decline in the incidence of KD and presenting symptoms among certain populations. The authors point out several limitations to the study, most notably the possibilities that some patients may have been misclassified as MIS-C instead of KD and vice-a-versa.

The overall conclusions drawn from this study reach beyond COVID-19 to a better understanding of the potential cause of KD, namely the involvement of the respiratory tract as the point of entry for agents that trigger KD.

David A. McLain, MD, MACR, FACP, FRCP

This is a very interesting study that looked at the incidence of Kawasaki Disease (KD), a disease with no known cause, before and during the COVID-19 pandemic with the associated quarantines and masking requirements that altered life as we knew it for a period of time. The authors found a decreased incidence of KD during this period of “isolation” that was significant, and then a rebound after the masking requirements were rescinded. The authors concluded that the results were consistent with a respiratory portal of entry for a trigger of KD.

That the incidence of rheumatic diseases can be influenced by environmental factors is of interest. Rheumatologists at Yale University led by Allen Steere, MD, and Stephen Malawista, MD, found the incidence of juvenile idiopathic arthritis was very high in the town of Lyme, Connecticut, and discovered the existence of Lyme disease that was later found to be tick-borne and due to a spirochete.

There was also a seasonal incidence to Lyme disease with two-thirds of the cases occurring in June, July or August. Seasonal incidence studies for rheumatic diseases were summarized by Schlesinger and Schlesinger in a review article published in July 2009 in Discovery Medicine. Their paper cited studies that found granulomatosis with polyangiitis, ANCA-associated glomerulonephritis and systemic vasculitis were more common from December to February.

A study from Denmark found the simultaneous occurrence of peaks of giant cell arteritis, polymyalgia rheumatica and respiratory infections over a 12-year period. Unfortunately, this is a difficult subject with studies in diverse areas of the world often showing totally different patterns of disease incidence — and we all know that association does not prove causality. Even so, pattern recognition in disease occurrence should be encouraged, as there may be a clue that will help solve the origin of a rheumatic condition.