Multisystem inflammatory syndrome (MIS)

Multisystem inflammatory syndrome (MIS) is a serious condition that occurs after a COVID-19 infection. With MIS, internal and external parts of the body, including the heart, lungs, kidneys, skin, eyes, and brain, become inflamed. MIS is divided into two types: MIS-C occurs in children and young adults up to age twenty-one, and MIS-A affects adults older than age twenty-one. Typically, the symptoms present similarly in adults and children, with a recent COVID-19 infection triggering this inflammatory response. Although MIS is rare in all age groups, it is more likely to affect school-age children than teenagers and adults.

Background

Multisystem inflammatory syndrome is a new condition that was first discovered during the COVID-19 pandemic. As early as April 2020, some children were presenting in hospitals worldwide with unusual symptoms that included a high fever, red eyes, a rash, and swollen hands and feet. This inflammatory condition also impacted multiple organs. During their treatment, the children tested positive for COVID, but their symptoms did not align with the disease. Initially, healthcare providers compared these symptoms to other inflammatory diseases, such as Kawasaki’s disease and toxic shock syndrome (TSS). However, they suspected that these symptoms were related to COVID-19. Initially, healthcare providers defined this set of symptoms as pediatric inflammatory multisystem syndrome, or PIMS. Later, the term was changed to multisystem inflammatory syndrome in children (MIS-C) and multisystem inflammatory syndrome in adults (MIS-A).

Overview

Healthcare providers continue to investigate the causes of MIS. Current evidence indicates that the syndrome is an inflammatory reaction to COVID-19 that typically occurs two to six weeks after the initial infection. Doctors do not yet know why MIS occurs and impacts only a small percentage of people who have been infected with COVID-19. Additionally, research indicates that MIS-C can affect children without other health conditions, although overweight or obese children might be at a heightened risk. MIS-C presents most frequently in school-age children, typically eight to nine years old, but has also occurred in younger children as well as adults.

Symptoms

MIS-C and MIS-A present with similar symptoms. Patients’ symptoms may vary, but a variety of common symptoms have been identified. Some are similar to the symptoms of Kawasaki disease, which is a heart condition that causes a high fever and inflammation of the blood vessels. Individuals with MIS may present with conjunctivitis, red eyes, red or swollen hands and feet, a body rash, swollen glands, and red cracked lips. Other symptoms are like those of TSS, including poor heart function or hemodynamic instability, which occurs when abnormal or unstable blood pressure impacts blood flow to internal organs.

Gastrointestinal upset is another common symptom of MIS and may be marked by abdominal pain, diarrhea, nausea, and vomiting. Respiratory symptoms common during COVID-19 are often reported in MIS-A patients, but children with MIS-C do not always have these symptoms. Additionally, individuals with MIS might experience shortness of breath, weakness, dizziness, headache, confusion, fatigue, and muscle pain.

Diagnosis

No diagnostic tests exist for MIS. As a result, healthcare providers must review the totality of the patients’ symptoms to properly diagnose the condition. Leading healthcare organizations, including the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP), have set forth guidelines to help healthcare providers promptly diagnose MIS-C or MIS-A in patients and expedite treatment.

The CDC established five criteria to diagnose a child with MIS-C. The patient must have a fever of 100.4 degrees Fahrenheit for at least twenty-four hours, and their bloodwork should show signs of inflammation. Other criteria include hospital treatment for multiple organ dysfunction and a current or past diagnosis of COVID-19. Additionally, other potential causes of inflammatory symptoms, such as bacterial infection, should be ruled out before making a definitive diagnosis of MIS-C.

The AAP offers similar guidance for healthcare providers to diagnose MIS-C. The organization recommends that providers evaluate pediatric patients for MIS-C if they present with a persistent fever, are moderately to severely ill, and have signs of organ dysfunction. Tests may include laboratory testing, chest radiographs, an electrocardiogram (EKG), and COVID-19 testing to further evaluate symptoms and make an accurate diagnosis. By following these guidelines, healthcare providers can more confidently diagnose cases of MIS-A or MIS-C.

Treatment

Although MIS can result in severe symptoms, it is treatable. Prompt medical care is essential to ensure a full recovery. MIS is caused by the body’s exaggerated immune response, so the treatment typically focuses on administering medication to suppress the body’s immune system to relieve symptoms. Treatment also helps to ease symptoms and reduce the risk of complications as the patient recovers. During their hospitalization, patients may receive intravenous fluids and antibiotics to maintain steady blood pressure and reduce the risk of bacterial infections. Upon hospital discharge, patients may be prescribed steroids to reduce inflammation and aspirin to protect the heart.

Prognosis

According to the CDC, most individuals with MIS recover quickly without any lasting effects on their overall health. Patients may have to stay in the hospital for several days to recover. If a patient experiences heart inflammation, they may need to complete some follow-up tests with a cardiologist.

Statistics

The CDC does not collect statistics on MIS-A because it is so rare. According to CDC data, as of August 2023, there have been 9,518 MIS-C cases in the United States since the pandemic began, as well as 79 deaths. Ninety-eight percent of children diagnosed with MIS-C had also been diagnosed with COVID-19, and the other 2 percent had been exposed to it. Additionally, 60 percent of all MIS-C cases occurred in males. The median age of MIS-C patients was nine years old, and half of all children with MIS-C were between five and thirteen years old.

Bibliography

“About MIS.” Centers for Disease Control and Prevention (CDC), 3 Jan. 2023, www.cdc.gov/mis/about.html. Accessed 29 Aug. 2023.

“COVID Data Tracker.” Centers for Disease Control and Prevention (CDC), covid.cdc.gov/covid-data-tracker/#mis-national-surveillance. Accessed 29 Aug. 2023.

“Hemodynamic Instability.” University of Miami Health, /umiamihealth.org/en/treatments-and-services/pediatrics/critical-care-(pediatrics)/hemodynamic-instability#:~:text=Hemodynamic%20instability%20occurs%20when%20there's,Chest%20pain. Accessed 29 Aug. 2023.

“Multisystem Inflammatory Syndrome in Children (MIS-C).” Yale Medicine, www.yalemedicine.org/conditions/multisystem-inflammatory-syndrome-in-children-mis-c. Accessed 29 Aug. 2023.

“Multisystem Inflammatory Syndrome in Children (MIS-C) Interim Guidance. American Academy of Pediatrics, 8 Feb. 2023, www.aap.org/en/pages/2019-novel-coronavirus-covid-19-infections/clinical-guidance/multisystem-inflammatory-syndrome-in-children-mis-c-interim-guidance/. Accessed 29 Aug. 2023.

Patel, Pragna, Jennifer DeCuir, Joseph Abrams, Joseph et al. “Clinical Characteristics of Multisystem Inflammatory Syndrome in Adults: A Systematic Review.” JAMA Network Open, 2021, jamanetwork.com/journals/jamanetworkopen/fullarticle/2784427. Accessed 29 Aug. 2023.

Sick-Samuels, Anna Christina. “MIS-C and COVID-19: Uncommon but Serious Inflammatory Syndrome in Kids and Teens.” John Hopkins Medicine, 8 Dec. 2021, www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/misc-and-covid19-rare-inflammatory-syndrome-in-kids-and-teens. Accessed 29 Aug. 2023.