Multisystem inflammatory syndrome in children — what parents need to know

While most children who get COVID-19 have a mild or even asymptomatic illness, some children may have a complication that can be severe and dangerous.

Called multisystem inflammatory syndrome in children (MIS-C) by the Centers for Disease Control and Prevention, it can lead to life-threatening problems with the heart and other organs in the body. Early reports compared it to Kawasaki disease, an inflammatory illness that can lead to heart problems. But while some cases look very much like Kawasaki’s, others have been different. Experts think that MIS-C is likely a reaction of the body to either a current or past COVID-19 infection, as 99% of the children diagnosed with it tested positive for the virus that causes COVID-19, and the remaining 1% were exposed to someone with COVID-19.

While cases have been reported in infants through age 20, most have been in children between 1 and 14 years, with a median age of 9 years. It is slightly more common in boys than in girls. As is the case with COVID-19 infections generally, it is more common in Latino and Black children.

What are the symptoms of MIS-C?

Symptoms of MIS-C vary from case to case, but can include

• prolonged fever (more than a couple of days)
• rash
• conjunctivitis (redness of the white part of the eye)
• stomachache
• vomiting and/or diarrhea
• neck pain
• irritability and/or unusual sleepiness or weakness
• fatigue.

There are many other conditions that can cause these symptoms. For example, strep throat can cause fever and rash, and there are plenty of common viruses that cause stomachache, vomiting, and diarrhea. Doctors make the diagnosis of MIS-C based not just on these symptoms, but also on their physical examination as well as medical tests that check for inflammation and how organs are functioning.

What parents need to know about MIS-C

• It is rare. As of late May 2021, there have been about 3,700 reported cases of MIS-C. While this sounds like a lot, there have been nearly four million reported cases of COVID-19 in children, which means that MIS-C happens in less than 0.1% of cases. Parents should not panic if their child gets one of these symptoms, or if they are diagnosed with COVID-19.
• It is treatable. Doctors have had success using various treatments for inflammation, as well as treatments to support organ systems that are having trouble. While there have been some deaths, most children who have developed this syndrome have recovered.
• It is serious. That’s why it’s important to be vigilant. Call the doctor if your child develops symptoms on the list above, whether or not they have been diagnosed with COVID-19. It’s particularly important that you call, or go to the emergency room, if your child develops
  • trouble breathing
  • severe abdominal pain
  • chest pain or pressure that doesn’t go away
  • a change in the color of the skin, lips, or nailbeds to pale blue or gray
  • confusion or trouble staying awake.

Many parents worry about taking children who haven’t yet received a COVID-19 vaccine to a doctor’s office or hospital. That’s understandable, but it’s important not to let that fear endanger your child’s health. If you are worried about your child — for this or any reason — call your doctor. Together you can figure out how to get your child the care they need.

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For more information on coronavirus and COVID-19, see the Harvard Health Publishing Coronavirus Resource Center.