Background In April, 2020, clinicians in the UK observed a cluster of children with unexplained inflammation requiring admission to paediatric intensive care units (PICUs). We aimed to describe the clinical characteristics, course, management, and outcomes of patients admitted to PICUs with this condition, which is now known as paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS). MethodsWe did a multicentre observational study of children (aged <18 years), admitted to PICUs in the UK between April 1 and May 10, 2020, fulfilling the case definition of PIMS-TS published by the Royal College of Paediatrics and Child Health. We analysed routinely collected, de-identified data, including demographic details, presenting clinical features, underlying comorbidities, laboratory markers, echocardiographic findings, interventions, treatments, and outcomes; serology information was collected if available. PICU admission rates of PIMS-TS were compared with historical trends of PICU admissions for four similar inflammatory conditions (Kawasaki disease, toxic shock syndrome, haemophagocytic lymphohistiocytosis, and macrophage activation syndrome). Findings 78 cases of PIMS-TS were reported by 21 of 23 PICUs in the UK. Historical data for similar inflammatory conditions showed a mean of one (95% CI 0•85-1•22) admission per week, compared to an average of 14 admissions per week for PIMS-TS and a peak of 32 admissions per week during the study period. The median age of patients was 11 years (IQR 8-14). Male patients (52 [67%] of 78) and those from ethnic minority backgrounds (61 [78%] of 78) were over-represented. Fever (78 [100%] patients), shock (68 [87%]), abdominal pain (48 [62%]), vomiting (49 [63%]), and diarrhoea (50 [64%]) were common presenting features. Longitudinal data over the first 4 days of admission showed a serial reduction in C-reactive protein (from a median of 264 mg/L on day 1 to 96 mg/L on day 4), D-dimer (4030 µg/L to 1659 µg/L), and ferritin (1042 μg/L to 757 μg/L), whereas the lymphocyte count increased to more than 1•0 × 10⁹ cells per L by day 3 and troponin increased over the 4 days (from a median of 157 ng/mL to 358 ng/mL). 36 (46%) of 78 patients were invasively ventilated and 65 (83%) needed vasoactive infusions; 57 (73%) received steroids, 59 (76%) received intravenous immunoglobulin, and 17 (22%) received biologic therapies. 28 (36%) had evidence of coronary artery abnormalities (18 aneurysms and ten echogenicity). Three children needed extracorporeal membrane oxygenation, and two children died.Interpretation During the study period, the rate of PICU admissions for PIMS-TS was at least 11-fold higher than historical trends for similar inflammatory conditions. Clinical presentations and treatments varied. Coronary artery aneurysms appear to be an important complication. Although immediate survival is high, the long-term outcomes of children with PIMS-TS are unknown.Funding None.

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Measurements and Main Results: De-identified data collected as part of routine clinical care was analysed. All children were diagnosed and staged for AKI based on the level of serum creatinine above the upper limit of reference interval (ULRI) values according to published guidance. Severe AKI was defined as stage 2/3 AKI. Uni-and multi-variable analyses were performed to study the association between demographic data, clinical features, markers of inflammation and cardiac injury, and severe AKI. Over the study period, 116 patients with PIMS-TS were admitted to 15 UK PICUs. Any-stage AKI occurred in 48/116 patients (41.4%), and severe AKI in 32/116 (27.6%) patients, which was mostly evident at admission (24/32, 75%). In univariable analysis, body mass index, hyperferritinemia, high C-reactive protein (CRP), Pediatric Index of Mortality 3 (PIM3) score, vasoactive medication and invasive mechanical ventilation (IMV) were associated with severe AKI. In multivariable logistic regression, hyperferritinemia was associated with severe AKI (compared to non-severe AKI, adjusted odds ratio 1.04, 95% CI 1.01-1.08, p=0.04). Severe AKI was associated with longer PICU stay (median 5 days [IQR 4,7] vs 3 days [IQR 1.5,5], p<0.001) and increased duration of IMV (median 4 days [IQR 2,6] vs 2 days [IQR 1,3], p=0.04). Conclusions: Severe AKI occurred in just over a quarter of children admitted to UK PICUs with PIMS-TS. Hyperferritinemia was significantly associated with severe AKI. Severe AKI was associated with increased duration of stay and ventilation. Although short-term outcomes for AKI in PIMS-TS appear good, long-term outcomes are unknown.

Medium-to long-term outcomes of the novel pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) 1 or multisystem inflammatory syndrome in children (MIS-C) are unknown. Short-term, 40-day, and 6-month outcomes have been published previously. [2][3][4][5]

The COVID‐19 pandemic potentially makes treatment of acute leukaemia more difficult. Most induction chemotherapy regimens for acute leukaemia lead to extended periods of cytopaenia and immunosuppression rendering patients vulnerable to opportunistic infections. As with many aspects of SARS‐CoV‐2, there is no universally accepted way of treating patients who present with acute leukaemia and associated infection.