DEAR MAYO CLINIC: I have been hearing about this pediatric syndrome that affects children with COVID-19. A friend recently said it can affect adults, too. Can you explain what these syndromes are and what I need to do to keep my family safe?

ANSWER: Although children of all ages can become sick with COVID-19, most kids who are infected typically have a mild illness. Some children who have an active infection with the virus that causes COVID-19 might not show any signs or symptoms. But, as you have heard, there is a condition developing in some children that is linked to COVID-19.

Multisystem inflammatory syndrome in children (MIS-C) is a serious condition in which some parts of the body, such as the heart, blood vessels, kidneys, digestive system, brain, skin or eyes, become inflamed. Inflammation typically includes swelling, often with redness and pain. The exact cause of MIS-C is not known, but it appears to be an excessive immune response related to COVID-19. Many children with MIS-C have a positive antibody test result. This means they've had a recent infection with COVID-19, even if they had a negative test.

In the U.S., more African American and Latino children have been diagnosed with MIS-C, compared with children of other races and ethnic groups. Studies are needed to determine why MIS-C affects these children more often. Factors may include differences in access to health information and services, as well as possible genetic risks. Most children with MIS-C are between 3 and 12, with an average age of 8. Some cases also have occurred in older children and in babies.

Recently, the Centers for Disease Control and Prevention published a report describing a multisystem inflammatory syndrome in adults (MIS-A).

Like MIS-C, MIS-A is a serious condition that can inflame some parts of the body, such as the heart, blood vessels, kidneys, digestive system, brain, skin or eyes. Inflammation typically includes swelling, often with redness and pain.

Presently, the typical case is someone who comes in with rapidly deteriorating multiorgan failure with little to no respiratory symptoms. And the reason for that is they've been infected within the past two to six weeks, but they are not infected now. They have developed antibodies, despite having been tested and showing negative results. Unfortunately, it's not yet known what causes this to occur and what can be done about it.

What makes the situation challenging is that people can develop this multisystem inflammatory syndrome weeks after the infection, during what appears to be recovery mode. And that's an unusual thing for a viral infection.

You can be assured that research is underway daily to learn more about COVID-19 and multisystem inflammatory syndromes. Experts continue to collect and analyze data about these complex conditions to learn more about possible causes, and improve diagnosis, treatment and outcomes. Every week, more is being learned about the incredible harm that this virus is capable of, and that is really another reason why this virus should not be taken likely.

Be aware of the signs and symptoms of multisystem inflammatory syndrome. Common symptoms for both children and adults can include:

• Fever that lasts 24 hours or longer.
• Vomiting.
• Diarrhea.
• Stomach pain.
• Skin rash.
• Red eyes.
• Redness or swelling of the lips and tongue.
• Feeling unusually tired.
• Redness or swelling of the hands or feet.

Emergency warning signs of multisystem inflammatory syndrome can include:

• Severe stomach pain.
• Cardiac symptoms, including chest pain, palpitations and shortness of breath.
• Bluish lips or face.
• Mental confusion.
• Inability to wake up or stay awake.
• Abdominal pain with vomiting and diarrhea.
• Skin rash and swelling of extremities.
• Faintness and low blood pressure that is new.

If you or a loved one experiences any of the emergency warning signs, seek care immediately.

People are getting COVID-19 fatigue, and much of the recent rise in case numbers is due to community spread of the infection. Taking precautions to prevent the spread of COVID-19 is critical, particularly as the virus continues to evolve. The best defense against multisystem inflammatory syndromes is to remain vigilant. Continue to wear a mask, maintain physical distancing and disinfect high-touch surfaces daily. Get vaccinated for the flu, wash your hands regularly and stay away from others if you are feeling ill. — Dr. Gregory Poland, Infectious Diseases, Mayo Clinic, Rochester, Minnesota

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Information in this post was accurate at the time of its posting. Due to the fluid nature of the COVID-19 pandemic, scientific understanding, along with guidelines and recommendations, may have changed since the original publication date. 

For more information and all your COVID-19 coverage, go to the Mayo Clinic News Network and mayoclinic.org.

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