This is the best description I've found regarding the Kawasaki symptoms (copied from the interwebs):
EPIDEMIOLOGY OF PIMS
On April 27 the UK put out an alert: a rising number of cases of children were requiring intensive care with marked inflammation of multiple organ systems, most of whom had tested positive for either the virus or antibodies to it. Since then, over 100 children in the US have been diagnosed, the majority in New York, in at least 10 states, with cases recognized elsewhere in Europe as well.
A 14 year old boy in England has died, and three children in New York have died as of today (5/10/20).
Of the first 8 British cases reported in the Lancet (1), 6 were of African decent, 1 was South Asian, and 1 was Middle Eastern; ages were 4-14. None were Caucasian, which is of course the largest population group in the UK. Race-specific numbers in the US have not been released.
PIMS is now a reportable disease in New York State (2): any suspected case must be immediately tested for COVID-19 (including serology), isolated, and reported into the state emergency health system.
A CYTOKINE TEMPEST IN A TEACUP
PIMS is, in a nutshell, runaway systemic inflammation. It's a cytokine "tempest in a teacup": a storm, raging in a child-sized body. It can result in vascular collapse, where a child can no longer maintain an adequate blood pressure. And it involves inflammation of many different organs- including the heart.
The symptoms- especially the cardiac inflammation- are very similar to a mysterious (but common) entity called Kawasaki Disease. The cause of Kawasaki's is still unknown, but it occurs exclusively in children, and causes inflammation in the medium-sized arteries throughout the body (including the coronary arteries of the heart, which can dilate out- become aneurysms- and kill the child). A "post-viral" response has ALWAYS been floated as the ultimate underlying cause for Kawasaki's, so perhaps we're just now proving that.
Some children with post-COVID PIMS look exactly like Kawasaki's, down to the "strawberry tongue" and red, cracked lips we all memorize as classic features in medical school. Perhaps indeed they are Kawasaki's. Some present with GI inflammation (so, crampy pain and diarrhea). Some present in a state of shock/collapse (so, like Toxic Shock Syndrome, with a coagulopathy to boot). Very few show features of lung inflammation- quite different from adults.
And many do develop the feared complication of a compromised heart: very low cardiac output, very low ejection fraction on echocardiography (meaning, the heart is squeezing out very little blood each time it beats), and some show the aneurysms.
WHAT'S SARS-CoV-2 HAVE TO DO WITH IT?
The full name of the disorder is "P(a)ediatric Multisystem Inflammatory Syndrome temporally associated with COVID-19." Children- to be very clear- still do VERY well with COVID-19, compared to adults. Children- under the age of 15 or so- still function EPIDEMIOLOGICALLY very differently from older people (mostly viral "dead ends.") But a small subset, once infected, will mount a pathologically overactive immune response.
This can occur while actively infected-- so, a PCR test for virus will be positive-- or it can occur post-infection, when a serology test will be positive. In the latter case, it's perhaps that the immune system has been "primed"-- raring to go, cruising for a bruising, eager for battle-- and decides to attack the body as opposed to the virus.
Or perhaps viral antigens hang around in a child's tissues (even if active infectious virus isn't still replicating) and the immune system, chock full o'antibodies, recognizes the target and attacks.
It might be too- in hotspots- that upon RE-EXPOSURE to the virus, the immune response is disproportional. Say a child had the virus, fought it off, had a mild case, and recovered. Now they come into contact with it again (in an area with high prevalence and lots of infected people)-- NOW it's ready to go.
CAN IT BE TREATED?
Yes! Shock is shock, and is treated with supportive ICU care. The same drugs given to suppress adult cytokine storms with COVID-19 are given to children with PIMS. Most do well, with supportive care (3).
EVERYTHING IS EVOLVING
It's a new virus. Is this something coronaviruses do? SARS and MERS infected very few people- and even fewer children-- so who knows if they would have caused similar problems-- but there is a report of Kawasaki's and a coronavirus from 2005 (4). What about genetics? This wasn't reported in China, but what was true in the Chinese population might not be true in populations of different ethnic and genetic backgrounds. As the virus whirls around the globe, it will continue to teach us- and give up its secrets.
SOURCES
1) Shelley Riphagen, Xabier Gomez, Carmen Gonzalez-Martinez, Nick Wilkinson, Paraskevi Theocharis. Hyperinflammatory shock in children during COVID-19 pandemic. Lancet.
https://doi.org/10.1016/ S0140-6736(20)31094-1
2) NYC guidelines:
3) Full case definition from the NHS, with treatment:
4) Frank Esper, Eugene D Shapiro, Carla Weibel, David Ferguson, Marie L Landry, Jeffrey S Kahn. Association Between a Novel Human Coronavirus and Kawasaki Disease. Infect Dis 2005 Feb 15;191(4):499-502.
Image: Getty Images