Paediatric Inflammatory Multisystem Syndrome (PIMS) is a serious, delayed post-infectious complication seen in children and adolescents. The syndrome involves a profound inflammatory response that follows a preceding illness, often one that was mild or even asymptomatic. PIMS presents a distinct health risk in the weeks following a common viral infection. Though rare, its potential for rapidly progressing to severe illness underscores the need for awareness and prompt medical attention.
Defining PIMS and its Link to Viral Infection
PIMS is defined as a hyper-inflammatory syndrome where the body’s immune system overreacts, leading to inflammation in multiple organ systems. The syndrome is a delayed consequence, typically appearing two to six weeks after the initial infection has resolved. This exaggerated immune response can affect various parts of the body, including:
- The heart
- Kidneys
- Lungs
- Brain
- Skin
- Eyes
- Gastrointestinal tract
The condition is strongly associated with prior infection by SARS-CoV-2, the virus responsible for COVID-19. Because of this link, PIMS is often referred to by the Centers for Disease Control and Prevention (CDC) as Multisystem Inflammatory Syndrome in Children (MIS-C).
Scientific evidence suggests this is a post-infectious process, meaning the body develops the syndrome after the virus has largely cleared. Many affected children test positive for SARS-CoV-2 antibodies, indicating past exposure, but negative for active infection via PCR testing at the time of PIMS presentation. The underlying cause is thought to be immune dysregulation, where the body’s defense mechanisms become overly activated, resulting in a systemic inflammatory state that damages various tissues and organs.
Recognizing the Clinical Manifestations
A prolonged and persistent fever, often lasting three to four days or more, is the most consistent initial sign of PIMS. This fever is usually accompanied by other signs of systemic inflammation affecting multiple parts of the body. The combination of symptoms, rather than any single symptom in isolation, raises suspicion for PIMS.
Gastrointestinal symptoms are very common, including severe abdominal pain, vomiting, and diarrhea. The pain can be significant enough to mimic conditions like appendicitis. A rash, which is highly variable in appearance, is also frequently observed.
Other notable signs include red or bloodshot eyes (conjunctivitis) and mucocutaneous changes. These changes often present as a “strawberry tongue,” swollen hands or feet, or red, cracked lips. Children may also experience extreme tiredness, muscle aches, headaches, and irritability. In severe cases, signs of poor circulation, such as cold hands, pallor, or confusion, can develop quickly, requiring immediate medical attention.
Medical Evaluation and Diagnostic Criteria
Diagnosing PIMS requires a combination of clinical assessment, laboratory testing, and the exclusion of other diseases, such as bacterial sepsis or toxic shock syndrome. There is no single definitive test; instead, doctors look for a specific pattern of findings. The initial evaluation involves documenting persistent fever and the involvement of at least two organ systems.
Specific blood tests check for markers of severe inflammation and organ dysfunction. Inflammatory markers are typically significantly elevated, including:
- C-reactive protein (CRP)
- Ferritin
- Erythrocyte sedimentation rate (ESR)
- Elevated D-dimer level, indicating coagulation abnormalities
Blood work may also show changes in cell counts, such as lymphopenia (low lymphocytes) and neutrophilia (high neutrophils).
A detailed cardiac evaluation is routine due to the frequent involvement of the heart. This often includes an echocardiogram to assess heart muscle function and look for abnormalities in the coronary arteries. Elevated levels of cardiac enzymes, such as troponin or N-terminal pro-B-type natriuretic peptide (NT-proBNP), also suggest myocardial injury. The diagnosis is established when these clinical and laboratory findings are present, other causes are ruled out, and there is evidence of a recent SARS-CoV-2 infection, usually through positive antibody testing.
Therapeutic Interventions and Supportive Care
The main objectives for treating PIMS are to rapidly reduce excessive inflammation and prevent damage to affected organs. Given the potential for rapid deterioration, many children require admission to an intensive care unit for close monitoring. Treatment protocols focus on immunomodulatory therapy to calm the overactive immune system.
The two primary classes of medication used are intravenous immunoglobulin (IVIG) and corticosteroids. IVIG, a blood product containing pooled antibodies, is often administered as a single, large dose (2g/kg) to modulate the immune response. Corticosteroids, such as methylprednisolone, are potent anti-inflammatory drugs that suppress the immune system’s activity.
Combining IVIG with corticosteroids, particularly in children with more severe illness, has been shown to better protect the heart and reduce the need for subsequent treatments. Supportive care is equally important and includes managing fluid balance, maintaining blood pressure with inotropes if necessary, and providing respiratory support. Low-dose aspirin is also commonly prescribed to reduce the risk of blood clots and coronary artery problems, often continued for several weeks after the acute illness has passed.