Researchers found that young patients with acute paediatric inflammatory multisystem syndrome temporally associated with Sars-CoV-2 infection (PIMS-TS) have raised levels of molecules, called cytokines, and reduced levels of infection-fighting white blood cells, called lymphocytes.
While cytokines help the immune system suppress infection, overproduction of these molecules can cause severe inflammation, which can harm the patient.
The scientists said their findings, published in the journal Nature Medicine, could contribute towards developing treatments that may help patients with the condition.
Dr Michael Carter, of Evelina London Children’s Hospital, who is first author on the study, said: “The support of children and young people with PIMS-TS was crucial in this study.
“Their help enabled us to monitor changes in the immune system during their illness and recovery and may contribute towards developing targeted immune therapy for children with PIMS-TS in the future.”
Symptoms of PIMS-TS include a rash, fever and abdominal pain. It causes severe inflammation in blood vessels, which can lead to heart damage.
The scientists analysed blood samples from 25 children who had PIMS-TS and compared them with samples from healthy children.
They found that young patients with PIMS-TS have raised levels of cytokines and reduced levels of lymphocytes, which gradually returned to normal once the children had recovered.
While initial reports suggested the condition may be similar to another childhood condition known as Kawasaki disease, the researchers said PIMS-TS appears to be distinct from the paediatric inflammatory syndrome.
Dr Manu Shankar-Hari, a consultant in intensive care medicine at Guy’s and St Thomas’ NHS Foundation Trust, who led the research, said: “PIMS-TS is a new syndrome.
“Our research has allowed us to provide the first description of the profound immune system changes in severely ill children with this new illness.
“These immune changes are complex. The innate, otherwise known as the rapidly responding, immune cells are activated.
“The lymphocytes, a particular type of white cell involved in specific protective immunity, are depleted, but appear to be actively fighting infection.
“Clinically, these children respond to treatments that calm the immune system such as corticosteroid and immunoglobulins.
“Although there are similarities to existing conditions such as Kawasaki disease, these clinical and immunological changes that we observe imply that PIMS-TS is a distinct illness associated with Sars-CoV-2 infections.”