Multisystem inflammatory syndrome in children (MIS-C) is a serious condition that appears to be linked to coronavirus disease 2019 (COVID-19). Most children who become infected with the COVID-19 virus have only a mild illness. But in children who go on to develop MIS-C, some organs and tissues — such as the heart, lungs, blood vessels, kidneys, digestive system, brain, skin or eyes — become severely inflamed. Signs and symptoms depend on which areas of the body are affected.

MIS-C is considered a syndrome — a group of signs and symptoms, not a disease — because much is unknown about it, including its cause and risk factors. Identifying and studying more children who have MIS-C may help to eventually find a cause. The U.S. Centers for Disease Control and Prevention (CDC) and the National Institutes of Health are working with doctors and researchers across the country to learn more about risk factors for MIS-C, share data, and improve diagnosis and treatment of MIS-C.

Rarely, some adults develop signs and symptoms similar to MIS-C. This new and serious syndrome, called multisystem inflammatory syndrome in adults (MIS-A), occurs in adults who were previously infected with the COVID-19 virus and many didn't even know it. MIS-A seems to occur weeks after COVID-19 infection, though some people have a current infection. If MIS-A is suspected, a diagnostic or antibody test for COVID-19 can help confirm current or past infection with the virus, which aids in diagnosing MIS-A.

MIS-C is rare, and most children who have it eventually get better with medical care. But some kids rapidly get worse, to the point where their lives are at risk.

Much remains to be learned about this emerging inflammatory syndrome. If your child shows any signs or symptoms, get help fast.

Signs and symptoms of multisystem inflammatory syndrome in children (MIS-C) include those below, though not all children have the same symptoms.

• Fever that lasts 24 hours or longer
• Vomiting
• Diarrhea
• Pain in the stomach
• Skin rash
• Feeling unusually tired
• Fast heartbeat
• Rapid breathing
• Red eyes
• Redness or swelling of the lips and tongue
• Redness or swelling of the hands or feet
• Headache, dizziness or lightheadedness
• Enlarged lymph nodes

Emergency warning signs of MIS-C

• Severe stomach pain
• Difficulty breathing
• Pale, gray or blue-colored skin, lips or nail beds — depending on skin tone
• New confusion
• Inability to wake up or stay awake

When to see a doctor

If your child has any of the emergency warning signs listed above — or is severely sick with other signs and symptoms — get care immediately. Take your child to the nearest emergency department or call 911 or your local emergency number.

If your child isn't severely ill but shows other signs or symptoms of MIS-C, contact your child's doctor right away for advice. Doctors may want to do tests — such as blood tests, or imaging tests of the chest, heart or abdomen — to check for areas of inflammation and other signs of MIS-C.

The exact cause of MIS-C is not known yet, 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 the COVID-19 virus. Some may have a current infection with the virus.

In the U.S., more Black and Latino children have been diagnosed with MIS-C compared with children of other races and ethnic groups. Studies are needed to help determine why MIS-C affects these children more often than others. Factors may include, for example, differences in access to health information and services as well as the possibility of risks related to genetics.

Most children with MIS-C are between the ages of 3 and 12 years old, with an average age of 8 years old. Some cases have also occurred in older children and in babies.

Many specialists consider MIS-C to be a complication of COVID-19. Without early diagnosis and appropriate management and treatment, MIS-C can lead to severe problems with vital organs, such as the heart, lungs or kidneys. In rare cases, MIS-C could result in permanent damage or even death.

In the U.S., the Pfizer-BioNTech COVID-19 vaccine is now available to people age 12 and older. A vaccine can prevent you or your child from getting the COVID-19 virus. If you or your child gets COVID-19, a COVID-19 vaccine could or prevent you or your child from becoming seriously ill. Also, if you and your child have been fully vaccinated, you and your child can return to many activities you may not have been able to do because of the pandemic — including not wearing a mask or social distancing — except where required by a rule or law.

If you or your child haven’t been vaccinated, you can take many steps to prevent yourselves from getting the COVID-19 virus and spreading it to others. The CDC recommends following these precautions for avoiding exposure to the virus that causes COVID-19:

• Keep hands clean. Wash hands often with soap and water for at least 20 seconds. If soap and water aren't available, use a hand sanitizer that contains at least 60% alcohol.
• Avoid people who are sick. In particular, avoid people who are coughing, sneezing or showing other signs that indicate they might be sick and contagious.
• Practice social distancing. This means that you and your child should stay at least 6 feet (2 meters) from other people when outside of your home.
• Wear cloth face masks in public settings. When in indoor public places or outdoors where there is a high risk of COVID-19 transmission, such as at a crowded event or large gathering, both you and your child — if he or she is at least 2 years old — should wear face masks that cover the nose and mouth. Further mask guidance differs depending on whether you are fully vaccinated or unvaccinated.
• Avoid touching your nose, eyes and mouth. Encourage your child to follow your lead and avoid touching his or her face.
• Cover your mouth with a tissue or your elbow when you sneeze or cough. You and your child should practice covering your mouths when you sneeze or cough to avoid spreading germs.
• Clean and disinfect high-touch surfaces every day. This includes areas of your home such as doorknobs, light switches, remotes, handles, countertops, tables, chairs, desks, keyboards, faucets, sinks and toilets.
• Wash clothing and other items as needed. Follow manufacturers' instructions, using the warmest appropriate water setting on your washing machine. Remember to include washable plush toys.

Some children with MIS-C test negative for a current infection with the COVID-19 virus. This means they don't currently have the virus that causes COVID-19. Yet evidence indicates that many of these children were infected with the COVID-19 virus in the recent past, as shown by positive antibody test results.

An antibody test with a positive result means that the child's immune system developed blood proteins (antibodies) that fought the COVID-19 virus. Sometimes this blood test is the only indication that the child was ever infected — meaning that the child may have fought the infection without ever having signs or symptoms of COVID-19. Still, some children with MIS-C are currently infected with the virus that causes COVID-19. This is usually confirmed by detection of the virus on a swab taken from the back of the nose or throat.

In addition to doing antibody testing and a clinical assessment, doctors may order some of these tests to look for inflammation and other signs of MIS-C:

• Lab tests, such as blood and urine tests, including tests that look for an abnormal level of inflammatory markers in the blood
• Imaging tests, such as a chest X-ray, an echocardiogram, an abdominal ultrasound or a CT scan
• Other tests, depending on signs and symptoms

Inflammation can seriously affect the heart, blood vessels, kidneys, digestive system, brain, skin or eyes.

When doctors suspect MIS-C, they need to rule out active cases of COVID-19 as well as other inflammatory conditions such as Kawasaki disease, sepsis or toxic shock syndrome, for early diagnosis and proper treatment.

Most children with MIS-C need to be treated in a hospital. Some need treatment in a pediatric intensive care unit. Treatment usually involves supportive care and measures to reduce inflammation in any affected vital organs to protect them from permanent damage. Treatment depends on the type and severity of symptoms and which organs and other parts of the body are affected by inflammation.

Supportive care may include:

• Fluids, if levels are too low (dehydration)
• Oxygen to help with breathing
• Blood pressure medications to normalize low blood pressure related to shock or to help with heart function
• A breathing machine (ventilator)
• Medications that reduce the risk of blood clots, such as aspirin or heparin
• In very rare cases, extracorporeal membrane oxygenation (ECMO) using a machine that does the work of the heart and lungs
• Other types of care

Treatment to reduce swelling and inflammation may include:

• Antibiotics
• Steroid therapy
• Intravenous immunoglobulin (IVIG), a blood product made up of antibodies
• Other types of treatment, such as targeted therapies aimed at reducing high levels of proteins called cytokines, which can cause inflammation

There is no evidence that MIS-C is contagious. But there's a chance that your child could have an active infection with the COVID-19 virus or another type of contagious infection. So the hospital will use infection control measures while caring for your child.

If your child is seriously ill with MIS-C, you may feel overwhelming anxiety and fear. Because MIS-C is rare, you likely don't know anyone who has been through this experience. To help cope with the emotional toll this can take, ask for support. This can range from discussing your feelings with loved ones and friends to asking for help from a mental health professional. Ask your health care team for advice. For your own sake and that of your child, don't try to handle this anxiety and distress by yourself.

Do the best you can to take care of yourself by getting enough healthy food, sleep and physical activity. Try stress management techniques, such as deep breathing, stretching and meditation, to help you through these difficult times.

If your child shows any emergency warning signs of MIS-C or is severely sick with other signs and symptoms, take your child to the nearest emergency department or call 911 or your local emergency number. Remember to wear a mask to protect yourself and others.

If your child's symptoms are not severe, contact your child's pediatrician or other health care professional. He or she may want to assess your child or refer you immediately to an infectious disease specialist.

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance. Make a list of:

• Your child's symptoms, including when they started
• Key personal information, including major stresses, recent life changes and family medical history
• All medications, vitamins or other supplements your child takes, including the dosages
• Any group activities your child recently participated in, including the dates
• Questions to ask the doctor

What to expect from your doctor

vYour doctor is likely to ask you — and your child, depending on his or her age — several questions, such as:

• When did the symptoms begin?
• How severe are the symptoms?
• Has your child been tested for COVID-19?
• Has your child been exposed to anyone who tested positive for the COVID-19 virus?
• Does your child go to school?
• Has your child been involved in any recent group activities, such as sports?
• Who has your child been in close contact with recently?

Preparing for the appointment can help ensure that you have time to get all of your questions answered and learn what the next steps are and why they're important.