The multisystem inflammatory syndrome is rare but possible in adults who recover from COVID-19, say researchers.

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The condition has, so far, been detected only in children. The researchers from the University of Calgary in Canada's Alberta stressed the need for clinicians to suspect multisystem inflammatory syndrome in adults when a patient has prolonged fever, with multiorgan involvement, after recovery from SARS-CoV-2 infection, the virus causing COVID-19.

The team described the possibility of the syndrome in adults in a study published in CMAJ (Canadian Medical Association Journal). The team described a 60-year-old man, who had tested positive for SARS-CoV-2 four weeks before, and visited the hospital for a range of symptoms, including prolonged shortness of breath, high fever, swelling and severe fatigue. Tests found an enlarged heart and lung swelling as well as other issues. "Given the patient's recent history of SARS-CoV-2 infection, fevers without localising symptoms, oral mucosal changes, cervical lymphadenopathy, conjunctivitis and lower extremity changes, we suspected inflammatory post-COVID-19 syndrome", wrote the team including Genevieve Kerkerian and Stephen Vaughan, infectious disease specialists from the varsity's Department of Medicine.

"The presentation was similar to reported cases of an uncommon but severe complication in children and adolescents infected with SARS-CoV-2, called multisystem inflammatory syndrome in children (MIS-C), as well as to Kawasaki-like illness", they added. Prompt initiation of medication helped the patient to recover. MIS-C was first described in April 2020 as a hyperinflammatory syndrome with features resembling Kawasaki disease. As of May 3, 2021, 3,742 children in the US had been formally diagnosed with MIS-C, with 35 related deaths. Much is unknown about the multisystem inflammatory syndrome in adults.

In October 2020, the US Centers for Disease Control and Prevention published a review of 27 adult cases that fit the description of a multisystem inflammatory syndrome. The preliminary case of MIS-A, described to date has been in patients younger than 50 years. "As we continue to learn about MIS-A, however, it is prudent not to assume any age limitation when considering the diagnosis, as our case suggests", the researchers said. "Unlike for MIS-C, there is currently no requirement to report cases of MIS-A to provincial or state authorities, but this should be encouraged to facilitate research and improve patient outcomes", the authors noted.