Multisystem inflammatory syndrome occurs in adults as well as children after COVID-19 infection
COVID 19 is increasingly recognised to trigger critical inflammatory and hyperinflammatory illness across the age spectrum. Paediatric Multisystem Inflammatory Syndrome – Temporally Associated with SARS-CoV-2 (PIMS-TS) [also known as Multisystem inflammatory syndrome] is reported in children and young people  However, this severe phenotype of COVID related inflammatory disease also affects adults, and therefore may present to adult medicine practitioners who may have little or no awareness of its clinical features. This poses a significant risk to patient care. As a group of collaborative adult specialists who have managed adults with multisystem inflammatory syndrome, we want to describe and highlight this condition to those working across general medicine, general surgery, cardiology, general practice and accident and emergency as well as other areas where these adults may present.
The clinical features of multisystem inflammatory syndrome in adults (MIS-A) present some time (usually weeks) after COVID-19 infection, so the diagnosis of COVID-19 may not be elicited and swabs for SARS-CoV-2 are expected to be negative. The clinical presentation is often acute, severe abdominal pain such that patients are triaged for surgical opinions or high, often unremitting fevers treated as sepsis refractory to antibiotics. MIS-A progresses with hyperinflammation leading to devastating cardiogenic shock. Key laboratory features may include raised inflammatory markers such as C-reactive protein, raised ferritin (>500), raised fibrinogen, and raised troponin and NT-pro-BNP. The full blood count may or may not be abnormal with lymphopenia, neutrophilia or low platelets seen in some cases . These tests may change rapidly and should be monitored daily. If recognised and treated promptly with high-dose immunosuppression these adults may go on to make a full recovery. Without recognition and treatment we can expect mortality and morbidity. There is no current evidence base to guide immune suppression but steroids and biologic drugs are currently used.
Characterisation of multisystem inflammatory disorders in children and young people is increasingly established. Since May 2020 the CDC have been tracking cases in children and have found 2060 cases with 30 deaths. Nearly 70% of these cases occurred in children who were Hispanic, Latino or Black . In the UK at the Evelina hospital in London a report of 70 cases found a higher proportion of patients were from minoritised groups . The Royal Society of Paediatrics and Child Health has highlighted the need to involve clinicians who specialise in immunology, infectious diseases, respiratory medicine, rheumatology, cardiology, intensive care, general paediatrics, haematology, and, in some cases, surgery, radiology, and neurology . The Evelina PIMS-TS working group created a guideline which is likely to also benefit those who present with MIS-A .
The presentation of this syndrome in adults is still emerging, but it should be considered by any clinician seeing adult patients who present acutely unwell with features above. Key in management is a collaborative approach across traditional borders and advice from local teams (especially those managing paediatric PIMS-TS/MIS-C) should be promptly sought. Further education on this topic would be beneficial to a great number of doctors across many medical specialities.
 Rubens et al, "Acute covid-19 and multisystem inflammatory syndrome in children," BMJ, p. 372:n385, 2021.
 CDC , "Case series of Multisystem Inflammatory Syndrome in Adults Associated with SARS-CoV-2 Infection - United Kingdom and United States, March - August 2020," 9 October 2020 . [Online]. Available: https://www.cdc.gov/mmwr/volumes/69/wr/mm6940e1.htm. [Accessed 7 March 2021].
 CDC, "Multisystem Inflammatory Syndrome in children (MIS-C). Cases in the US," 1 March 2021. [Online]. Available: https://www.cdc.gov/mis-c/cases/index.html. [Accessed 7 March 2021].
 White et al , "Paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS): the Evelina Experience," Archives of Disease in Chidhood , vol. 105, no. 11, 2020.
 Harwood et al , "A national consensus management pathway for paediatric inflammatory multisystem syndrome temporally associated with COVID-19 (PIMS-TS): results of a national Delphi process," The Lancet Child and Adolescent Health , vol. 5, no. 2, pp. 133-41, 2021.
 Evelina London, Clinical Guidance. Paediatric Critical Care: PIMS-TS Paediatric Multisystem Inflammatory Syndrome temporally associated with SARS-CoV2, London: Guy's and St Thomas' Hospital NHS foundation trust, 2020.
Competing interests: ALG was on the writing group for the ACTT-2 trial which utilised baricitinib. ALG holds or has held shares in various companies including pharmaceuticals or health as part of a portfolio and with no interest >0.01%.