In Costa Rica, a national public health organization announced towards the end of August that three children had been diagnosed with MIS-C. Cases of MIS-C had also been recorded in many other Latin American countries, including Argentina, Bolivia, Colombia, Cuba, the Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Uruguay, and Venezuela, as well as in Puerto Rico. News of a first confirmed case of PIMS-TS in Australia emerged (from Victoria) on 4 September, along with news of other suspected cases under review. In South Korea, news of two confirmed cases broke on 5 October (and the existence of a case dating back to the end of April was reported in November). A similar condition began to be recognized in some adults. In June, an adult case of a Kawasaki-like multisystem inflammatory syndrome following SARS-CoV-2 infection was described in a 54-year-old woman from Israel with no history of autoimmune disease, who experienced uveitis in both eyes. (A further suspected adult case was covered in the Israeli national press.) A case involving a 36-year-old Hispanic American woman with clinical features otherwise consistent with MIS-C was reported from New York. A diagnosis consistent with PMIS was also reported in a UK-born, 21-year-old man of Somali origin. A case report published in The Lancet regarding a 45-year-old Hispanic man who presented in New York with features strongly resembling MIS-C called for awareness of "a potential MIS-C-like condition in adults." Further reports of multisystem inflammatory syndrome linked to COVID-19 exposure emerged in adults.
In the meantime, different names and provisional case definitions are being used around the world. The initial case definitions released by the World Health Organization (WHO), the Royal College of Paediatrics and Child Health (RCPCH) and Centers for Disease Control and Prevention (CDC) all include involvement of more than one organ system, along with fever and elevated inflammatory markers. Criteria that vary among these three definitions include the ways in which involvement of different organs is defined, the duration of fever, and how exposure to COVID-19 is assessed. The preliminary WHO case definition is for "multisystem inflammatory syndrome (MIS) in children and adolescents temporally related to COVID-19" (box). The WHO has established a platform for standardized, anonymized clinical data, along with a dedicated case report form, and underlines the "urgent need for collection of standardized data describing clinical presentations, severity, outcomes, and epidemiology." Diagnostic guidance by the RCPCH proposes a broader case definition (for PIMS-TS), which was also endorsed by an expert panel convened by the American College of Cardiology. Key clinical criteria set out in the RCPHC case definition are: persistent fever, inflammation (indicated by neutrophilia, high CRP levels and low lymphocyte count), and evidence of organ dysfunction (shock; cardiac, respiratory, renal, gastrointestinal, or neurological disorder), coupled with additional clinical features, including laboratory, imaging and ECG findings. Coronary artery abnormalities, such as dilatation, may be apparent at echocardiography and ECG (or contrast CT of the chest). Biomarkers supporting the diagnosis include abnormal fibrinogen levels, high D-dimers (possible coagulopathy), high troponin, low albumin, and high ferritin.