ObjectivesHeart involvement in multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C) is a new challenging problem, requiring fast and reliable diagnostics and appropriate treatment. The aim of this study is to describe heart involvement in patients with MIS-C.Study DesignIn this retrospective, multicenter cohort study, data of 122 patients were included. All patients met WHO and CDC criteria of MIS-C.ResultsVarious types of heart involvement in MIS-C patients were observed. Patients with solely coronary artery lesions (CAL, n = 10, 8.2%) had typical features of Kawasaki disease: younger age, thrombocytosis and normal ferritin level, without giant CA aneurysms, thrombosis, myocardial infarction, shock, and ICU admission. Patients with solely myocardial involvement (MI, n = 30, 24.6%) had an older onset age, elevated ferritin, LDH, the highest D-dimer, H score, and thrombocytopenia level. The following clinical signs were associated with MI: gastrointestinal and central nervous system disorder, sore throat, swelling face, splenomegaly, shock, and treatment in the intensive care unit required. Patients with a combination of CAL and MI (n = 10, 8.2%) had symptoms similar to patients with solely MI, except for impressive thrombocytopenia. Shock and ICU admission were found in 34.7% of patients without heart involvement (n = 72, 59%). One major criterion [troponin > 32 pg/ml (52 points)] or at least two minor criteria [face swelling (32 points) and D-Dimer > 1,300 ng/ml (29 points)] were associated with MI (>32 points) with a sensitivity of 67.5% and a specificity of 88.9%.ConclusionThe above-suggested criteria can be added to routine diagnostic procedures to confirm MI in MIS-C patients.

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Background:Sakha Republic (Yakutia) - SR(Y) is a bid arctic region of Russia with high proportion of aboriginals - Yakutians (50%), intra-national marriages, increased level of inbreeding and high distribution of HLAB27 among aboriginals – 33%, according the epidemiological studies. The main type of arthritis is ankylosing spondylitis in adults and enthesytis-related arthritis (ERA) of juvenile idiopathic arthritis (JIA) in children. The pattern of arthritis distribution in adults and children in SR(Y) is differ from Caucasians and similar to Native Americans.Objectives:Our study aimed to evaluate the features of JIA in aboriginals of SR(Y), associated with high prevalence of HLAB27 antigen.Methods:In the retrospective study we included 144 Yakutians who were admitted in the rheumatology department of Yakutsk in 2007-2016 years and 753 JIA patients Caucasian origin in Saint-Petersburg in the same years. We evaluated routine clinical and laboratorial features. HLA B27 was evaluated according the clinical judgement of the attending physicians.Results:ERA is a main JIA category in Yakutians. The main features the male predominance, higher onset age, high inflammatory activity, lower number of active joints, high incidence of hip and sacroiliac joints involvement, lower levels of psoriasis and uveitis. Yakutians have rare the involvement of cervical spine (6% vs 14%, p=0.0000001), TMJ (1% vs 6%, p=0.027), elbow (8% vs 16%, p=0.012), wrist (18% vs 28%, p=0.017), MCP (7% vs 21%, p=0.00005), PIP (8% vs 25%, p=0.00005). The treatment rates of methotrexate and biologics were similar between groups, but in Yakutians the biologics were administered earlier, because methotrexate failed and often was ineffective. The cumulative probability to receive biologics was higher in Yakutians compare to Caucasians: HR=3.4 [2.6; 4.4], p=0.000001 (Figure 1). The main biologic in Yakutians was etanercept (49/70; 70%). Yakutians received corticosteroids and cyclosporine A rarely, due to low incidence of systemic onset JIA and oligoarthritis with uveitis. It was observed, that the HLA B27 as a risk factors had different significance in Yakutians and Caucasians. HLA B27 presence increased the risk of ERA OR=2.72 (1.3; 5.6) p=0.01 in Yakutians and OR=69.2 (29.5; 162.3), p=0.00001 for Caucasians; for biologic administration: 0,86 (0,4; 1,8), p=0.529 and 2,45 (1,5; 4,0), p=0.0003, respectively.Figure 1.Cumulative probability to leave without biologics between Yakutian and Caucasian JIA patients.Conclusion:High distribution of HLA B27 antigene in Yakutians, lead to different pattern of JIA categories distributions and patient’s management.This work was supported by the Project of the Ministry of Science and Higher Education of the Russian Federation (basic part of funding to M.K. Ammosov North-Eastern Federal University #FSRG-2020-0016) and by the RFBR grant #18-05-600035_Arctika.Table 1.Differences between Yakutian and Caucasian JIA patients.JIA featuresYakutians, n=144 (%)Caucasians, n=723 (%)рGender, boys, n (%)85 (59.0)279 (38.6)0.000006Onset age, years10.6 (6.0; 13.4)6.0 (3.0; 10.3)0.0000001JIA categories, n (%)Oligoarthritis36 (25.0)188 (26.0)0.0000001Poly, RF (-)21 (14.6)248 (34.3)Poly, RF (+)1 (0.7)22 (3.0)Systemic onset4 (2.8)53 (7.3)ERA76 (52.8)171 (23.7)Psoriatic arthritis6 (4.2)41 (5.7)Active joints4.0 (3.0; 6.0)6.0 (3.0; 12.0)0.0000001Uveitis, n (%)16 (11.1)114/503 (22.7)0.002Psoriasis, n(%)3/143 (2.1)46/719 (6.4)0.043Hip involvement50 (34.7)146 (20.2)0.0001Sacroiliitis46 (31.9)69 (9.6)0.0000001HLA B27, n (%)76/131 (58.0)105/301 (34.8)0.00001ANA, n (%)4/46 (8.7)204/444 (46.0)0.00001RF, n (%)3/141 (2.1)22/403 (5.5)0.104Biologics, primary, n (%)70/144 (48.6)347 (48.0)0.892Time before first biologics, years0.6 (0.3; 1.4)2.6 (1.0; 5.4)0.0000001Disclosure of Interests:None declared