Paediatric Inflammatory Multisystem Syndrome (PIMS) is a serious, yet rare, condition affecting children and adolescents. It is a delayed reaction, occurring weeks after an initial infection with SARS-CoV-2, the virus responsible for COVID-19. The syndrome involves an overactive immune response that causes widespread inflammation throughout the body. PIMS is a post-infectious complication that can lead to severe illness requiring immediate medical attention, even though most children experience only mild or asymptomatic COVID-19.
Understanding the Symptoms
The clinical presentation of PIMS is diverse, posing a diagnostic challenge for clinicians. The condition is defined by a high and persistent fever, typically lasting three days or more. This prolonged fever is often the first sign, and a mandatory criterion, for diagnosis.
PIMS is characterized by multisystem involvement, meaning multiple organ systems are affected by inflammation. Children often present with a rash of varying appearance and conjunctivitis (red eyes). Gastrointestinal symptoms are also common, frequently including severe abdominal pain, vomiting, and diarrhea, sometimes mimicking conditions like appendicitis.
Cardiovascular system dysfunction presents the most concerning symptoms. Patients may develop signs of shock, such as low blood pressure (hypotension), cold hands and feet, and a rapid heart rate. This results from inflammation affecting the heart muscle (myocarditis) or the blood vessel lining. Due to the wide array of symptoms, PIMS can resemble other serious childhood illnesses, including Kawasaki disease and toxic shock syndrome.
How Doctors Confirm the Condition
Diagnosing PIMS requires clinical suspicion, laboratory evidence of systemic inflammation, and confirmed SARS-CoV-2 exposure. Doctors must first rule out other causes of fever and multisystem presentation, such as bacterial sepsis or other infections. Blood tests are essential, looking for elevated markers of inflammation.
Specific inflammatory markers that are raised include C-reactive protein (CRP) and ferritin. Other indicators of the body’s overreaction are elevated D-dimer, suggesting abnormal blood clotting, and procalcitonin. Doctors also measure cardiac enzymes, such as troponin and B-type natriuretic peptide (BNP or pro-BNP), to look for evidence of organ injury, particularly in the heart.
Confirmation of recent or past SARS-CoV-2 exposure is necessary for the case definition. This is most often achieved through a positive antibody test, indicating the child’s immune system has previously encountered the virus. Less commonly, a positive viral swab (PCR test) or a clear history of close contact with someone who had COVID-19 provides the necessary link.
Imaging studies are also crucial, particularly an echocardiogram, which is an ultrasound of the heart. This test allows physicians to assess the heart’s pumping function and check for specific complications, such as dilation or aneurysm formation in the coronary arteries. The presence of these cardiac abnormalities strongly supports a diagnosis of PIMS and guides the urgency of treatment.
Managing the Illness and Recovery
Management of PIMS focuses on rapidly controlling inflammation to prevent permanent organ damage. Due to the potential for quick deterioration, most children require hospitalization, often in a pediatric intensive care unit (PICU), for close monitoring and supportive care. Treatment is centered on immunomodulatory therapies designed to calm the immune system’s overreaction.
The two main treatments are intravenous immunoglobulin (IVIG) and systemic corticosteroids, such as methylprednisolone. IVIG is a pooled product of human antibodies that helps reset the immune system. Corticosteroids work to reduce inflammation throughout the body. For patients who do not respond adequately to this initial dual therapy, doctors may escalate treatment to include biologic agents like anakinra or tocilizumab, which target specific inflammatory pathways.
The prognosis for children with PIMS is generally positive, with the vast majority recovering fully. However, the recovery trajectory involves careful long-term follow-up, especially for cardiac health. Echocardiograms are repeated at structured intervals, such as two and six weeks after discharge, to ensure that any initial coronary artery damage resolves.
While the acute inflammation typically subsides within the first month, some children experience lingering issues like physical deconditioning and fatigue. Psychological sequelae, including anxiety and post-traumatic stress symptoms, can also persist after a severe illness and lengthy hospital stay. Multidisciplinary follow-up care is therefore essential to monitor for these ongoing physical and mental health needs, ensuring a complete return to normal life.