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We first heard about severe inflammatory symptoms linked to children and COVID-19 back in spring. It was confusing event for infectious disease experts.

Now, the medical community has a clearer picture of the rare, but life-threatening condition.

“My stomach started having a sharp pain in it,” MIS-C patient Jalyn Williams said.

It was the end of July when Jalyn Williams’ mysterious symptoms came on quickly.

“My energy was very low. I didn’t want to do nothing, I didn’t want to get off the bed, I just wanted to lay down and sleep all day,” he said.

The 13-year-old was hot to the touch and complained of pain. His father immediately took him to a local hospital.

“By the time we got to the hospital, they checked his temperature and it was 105,” father Steve Williams said.

After two days and no improvement, Williams was transferred to Lurie Children’s Hospital and brought to the ICU.

“When Jalyn came in, he was actually very sick. When I first saw him, he was having very severe abdominal pain, severe neck pain,” Dr. Dan Balcarcel said. “It seemed that he did have an infection with the virus that causes COVID-19 several weeks before coming to the hospital.”

It was a major clue in Jalyn’s mysterious symptoms. But like many children, he never showed signs of having COVID-19.

Lab tests and infectious disease specialists determined the 13-year-old was suffering from MIS-C, which stands for Multi-system Inflammatory Syndrome. It’s a rare, exaggerated immune response that can occur in children several weeks after a COVID-19 infection.

“It’s actually quite rare compared to the number of pediatric patients who get infected with COVID-19, a very small number will go on to get MIS-C,” Dr. Balcarcel said.

MIS-C causes inflammation throughout the body and can leave to organ dysfunction along with heart, kidney and breathing problems.

It’s not known yet why some have gotten sick with MISC-C, while others have not.

“We know MIS-C is not contagious itself, so a patient with MIS-C is not contagious, they are past that period,” Dr. Balcarel said.

Doctors at Lurie administered IV steroids and a medication called IVIG to dampen Jalyn’s over-reactive immune response.

“I felt bad for him dealing with all that pain,” his father said.

So far, doctors at Lurie Children’s Hospital have cared for about a dozen children with MIS-C during the pandemic.

According to new data just released by the CDC, there have been 792 confirmed cases and 16 deaths related to the illness. The CDC is urging parents to watch for symptoms like fever, abdominal pain, vomiting, diarrhea, neck pain, rash, bloodshot eyes or fatigue.

After spending about a week in the hospital, Williams has been building up his strength.

“It’s nothing to play with it’s really bad it really hurt bad it’s pain I never had before and I don’t want no other kids to have the pain,” he said.

His doctors expect a full recovery with his inflammation levels and heart functions now normal. But they’ll follow him along long-term with the hope to learn much more about MIS-C and any possible lasting effects.