Dening Kawasaki Disease and Pediatric Multi-Inammatory Syndrome During SARS-CoV-2 Epidemic in Italy: Results From A National, Multicenter Survey.

Background: There is mounting evidence on the existence of a Pediatric Multi-inammatory Syndrome related to SARS-CoV-2 (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities. Methods: The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group – KDG) or KD-like (Kawacovid Group - KCG) disease. Demographic, clinical, laboratory data, treatment information, and patients’ outcome were collected in an online anonymized database (RedCAP (cid:0) ). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups Results: One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were signicantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis and 37,8% with hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated Ferritin and Troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p=0.04 and 71,9% vs 43,4%; p=0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p<0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p<0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data. Conclusion: Our study suggests that SARS-CoV-2 infection might determine two distinct inammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths.


Background
Italy was the rst Western Country to be hit by the SARS-CoV-2 epidemic. To date, more than 236000 cases have been diagnosed, with more than 32000 deaths. Children accounted for almost 2% of infections, with an estimated mortality rate of 0,2% 1 . These data con rm previous reports on lower rates of SARS-CoV-2 infection and milder forms of the disease in children, compared to adults [2][3][4] . Nonetheless, few weeks after the epidemic peak, an abnormally high number of severely ill children were seen in those areas of the country with higher SARS-CoV-2 incidence [5][6][7] ; these observations were then con rmed in other European countries [8][9][10] . There is now mounting evidence on the existence of a childhood multiin ammatory syndrome related to SARS-CoV-2 infection sharing some similarities with Kawasaki Disease (KD) and Toxic Shock Syndrome (TSS) 9 . This condition has been named such as Pediatric Multiin ammatory Syndrome temporally associated with COVID-19 (PIMS-TS) or Multisystem In ammatory Syndrome associated with Coronavirus Disease 2019 (MIS-C) 11,12 . However, the real extent of the clinical spectrum of disease, and the exact role of SARS-CoV-2 infection, are still poorly understood. Moreover, it is still not clear if SARS-CoV-2 might also be considered a trigger for KD development or if KD, during the SARS-CoV-2 epidemic, presented peculiar and unusual clinical manifestations.
Our study aimed to build a national survey for patients with KD or KD-like multisystemic disease during SARS-CoV-2 epidemic evaluating clinical manifestations, laboratory data, treatment, outcome, and relationship with virus outbreak.

Study Design and patient selection
This is an observational, retrospective, multicenter study. Institutional Review Board approval was achieved (IRCCS Burlo Garofolo-03/2020). The Rheumatology Study Group of the Italian Pediatric Society launched a national, online, survey on April 24 th, 2020 to enroll those patients diagnosed with KD or KD-like multisystemic disease during SARS-CoV-2 epidemic. The children hospitalized between February 1st 2020, and May 31st 2020 with the clinical diagnosis of classical or incomplete-KD (iKD) as well as KD-like multi-in ammatory syndrome were enrolled.
The clinical classi cation was: 1) KD and iKD diagnosis, named as Kawasaki Disease Group (KDG), based on the ful lment of the American Heart Association criteria 13 ; 2) KD-like multi-in ammatory syndrome diagnosis, named as KawaCOVID Group (KCG), based on the presence of i) persistent fever, lymphopaenia and evidence of single or multi-organ dysfunction with other additional clinical, laboratory or imagining; ii) exclusion of any other microbial cause 11 .
In consideration of the retrospective nature of the study, an expert panel of pediatric rheumatologists (AR, GS, CB, MC, RC), blinded for patients' recruiting center, was asked to review every patient included in the database to check the correct patient classi cation or eventually reclassify them properly. Those patients who did not ful ll any of the above-mentioned criteria were excluded from the study.

Data collection
Demographic, clinical, and laboratory data, treatment information, and patient outcome were collected in an online anonymized database which was built for the study purpose (RedCAP→). Data about complications and last follow-up after discharge were collected where available. Results from all tests for SARS-CoV-2 infection with an RT-PCR assay and/or with a serologic assay were also reported. Clinical data collected were part of the normal standard of care. Categorical variables are described as absolute frequency and percentage while continuous variables as   median and interquartile range. Chi square test or exact Fisher test were applied to evaluate the  association between two categorical variables while non parametric Wilcoxon Mann-Whitney test was used to study differences between two groups of a categorical variable on a continuous variable. A pvalue < 0·05 was considered as statistically signi cant. Statistical analysis was conducted using SAS software, Version 9·4 (SAS Institute Inc., Cary, NC, USA).

Results
Emails to more than 10000 members of the Italian Pediatric Society were sent. Data from 194 patients were entered into the database. After reviewing all the data for duplicates and les with missing information 159 cases were sent to the case de nition committee. 10 patients were excluded by the committee since they didn't ful ll the inclusion criteria. 149 patients with a nal diagnosis of KDG or KCG were included in the study. 69 patients satis ed KD criteria, 37 iKD criteria, and 53 KawaCOVID criteria. Among the 53 patients classi ed as KawaCOVID, 10 satis ed also KD or iKD criteria (7 and 3, respectively). The population consisted of 84 males and 65 females, the median age at the time of diagnosis was 3 years (IQR: 1-6 years). Sixty-four out of 149 patients reported at least one symptom in the three months before hospital admittance suggestive for SARS-CoV-2 infection; only one patient (with diarrhea and close contact to a con rmed SARS-CoV-2 patient) had a positive PCR nasal swab for SARS-CoV-2 one month before admission, while 29 patients were tested by nasal swab before disease onset for close contact with con rmed cases, but resulted negative.
Among KCG the use of IVIG alone, glucocorticoids alone or combined with IVIG at the time of diagnosis was not associated with a higher incidence of clinical worsening and/or presence of cardiac involvement at follow-up (data not shown).
Since SARS-CoV-2 spread with different prevalence through Italy, with Piedmont and Lombardy being the most heavily hit regions, we compared the data of patients from these two regions (76 patients) (Group A) with the data of patients from the other regions (73 patients) (Group B) irrespectively from diagnostic classi cation. Group A patients presented more often with diarrhea (36,8% vs 15,1%; p = 0,003), myocarditis (29,0% vs 9,6%; p = 0,003), pericarditis (15,8% vs 2,7%; p = 0,01) and hypotension/noncardiogenic shock (17,1% vs 2,7%; p = 0,01). Again, Group A patients were con rmed to be signi cantly older ( While the KDG cases were spread during the study period, the KCG cases were mainly concentrated towards the end of the observation period with about 1 month of delay compared to the peak of the SARS-CoV-2 epidemic (Fig. 3). neurological symptoms, prevalence of CAA, myocarditis, pericarditis, and valvular insu ciency) between KDG and KD-Historical group respectively. No difference was also found in laboratory data available (data not shown). KDG patients from highly endemic areas (Piedmont and Lombardy) were compared to those of medium-low endemic areas. No statistical difference was found in clinical manifestations and laboratory data between the two groups (data not shown).

Discussion
The occurrence of a severe pediatric in ammatory disease, with some characteristics of KD, has been described since late march, in areas with high SARS-CoV-2 incidence 5,7,9,15−18 . Whether this is a particularly aggressive form of KD triggered by SARS-CoV-2 or a completely different entity is still a matter of debate.
Although some case series have already been reported [15][16][17][18] , this is a national survey aimed to collect all patients affected by KD and those with KD-like in ammatory symptoms during SARS-CoV-2 epidemic.
Notably, after the rst cases of SARS-CoV-2 in the northern Italy regions, the lock-down policy reduced the spread of the infection through other regions.
We con rmed some clinical evidence already reported in the literature; KCG patients are older at disease onset and present more frequently gastrointestinal and respiratory symptoms 3 , while the classic mucocutaneous symptoms of KD were less common. Children in the KCG also showed higher markers of in ammation, with lower WBC, and platelets 7,8 . Indeed, lymphopenia is very common in patients with SARS-CoV-2. Accordingly, patients from the KCG were at higher risk of developing sHLH which is indeed rarely described in children with KD 20 .
Other authors compared patients with PIMS-TS or analogs with a historic cohort of KD patients obtaining similar results 7,9,16 ; the importance of our observation relies on the fact that out KDG was recruited during the same period of KCG with a controlled patients selection.
Patients from the KCG also had signi cantly longer hospitalization and higher probability to need ICU admittance, for the occurrence of shock, need of vasoactive agents, and invasive ventilation. In the UK, it has been recently reported a higher incidence of ICU admittance of patients with unexplained in ammatory conditions suggestive of PIMS-TS; it is important to underline that in this cohort 2 out of 78 children died 21 . No death was reported in our cohort. Although we did not nd any signi cant correlation between initial treatment and outcome at the end of follow-up, it is important to underline that the use of glucocorticoids was more frequent in KCG and that all KCG patients received glucocorticoids, IVIG or both within 24 hours since admission. This is to con rm that maybe a more aggressive treatment at the time of admission might prevent clinical complications or even death. We would suggest, in absence of stronger clinical evidence, that early treatment with both IVIG (2 gr/kg/day) and glucocorticoids (methylprednisone 2 mg/kg/day) is indicated in KawaCOVID patients; in our experience treatment with parenteral anakinra (from 2 mg/kg/day to 10 mg/kg/day) is indicated in those patients with rapid clinical worsening or if clinical improvement is not reached within 48 hours since starting IVIG and corticosteroids. Our hypothesis seems to be con rmed from Navallo-Millan et al., suggesting that anakinra could be bene cial in COVID-19 adult patients with evidence of cytokine storm syndrome when initiated early after the onset of Acute Hypoxic Respiratory Failure 22 .
Heart involvement is peculiar to both KDG and KCG 6,23 . The major complication in KDG patients was the occurrence of CAA while KCG patients were at higher risk to develop myocarditis with heart insu ciency and related manifestations, such as valvular insu ciency.  On the other hand, previous data suggested that patients with PIMS-TS have some peculiar characteristics when compared to classic KD patients or even KSS 7,9 . We suggest that SARS-CoV-2 might determine two types of in ammatory diseases in children: the rst manifestation is the classic KD, that could be triggered by the coronavirus, as already suggested 29 . According to our results, the occurrence of this SARS-CoV-2-triggered KD is rare and does not impact signi cantly on the annual incidence of the disease. The second manifestation related to SARS-CoV-2 exposure during childhood is the multisystem in ammatory syndrome, which affects older children and presents mainly with myocarditis, gastrointestinal symptoms, and the occurrence of shock. Since it appears this latter disease is distinct from KD we recognize the term KawaCOVID could be misleading and both PIMS-TS or MIS-C seem more appropriate. Age at SARS-CoV-2 infection, previous coronaviruses exposure 23 , host immunity, and predisposing genetics might have a role in determining which patients would develop a SARS-CoV-2 related disease.

Conclusions
Even though PIMS-TS/MIS-C is a severe disease, the majority of patients respond to treatments, with few complications and a good outcome. As prospective data on larger series are not available, our experience suggests a prompt treatment with glucocorticoids and IVIG. The use of anakinra is also to take into account if clinical worsening is present or in case of a lack of clinical response. Ongoing studies on the treatment of in ammatory conditions related to SARS-CoV-2 might help to de ne the best options for PIMS-TS patients 30

Consent for publication
Not applicable Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.