Multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children
Name	Multisystem inflammatory syndrome in children
Synonyms	MIS-C, paediatric inflammatory multisystem syndrome (PIMS)
Field	Pediatrics, infectious disease, Rheumatology
Symptoms	Persistent fever, rash, gastrointestinal distress, shock
Complications	Myocarditis, coronary artery aneurysm, acute kidney injury
Onset	2–6 weeks post-SARS-CoV-2 infection
Causes	Dysregulated immune response to COVID-19
Risks	Prior infection with SARS-CoV-2
Diagnosis	Based on WHO or CDC criteria, exclusion of other causes
Differential	Kawasaki disease, toxic shock syndrome, sepsis, macrophage activation syndrome
Treatment	Intravenous immunoglobulin, corticosteroids, biologic agents
Medication	Tocilizumab, Infliximab
Prognosis	Generally good with treatment; risk of cardiac sequelae

Multisystem inflammatory syndrome in children is a rare but serious condition characterized by widespread inflammation in multiple organ systems. It typically manifests several weeks after a child has been infected with SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The condition shares clinical features with other inflammatory syndromes like Kawasaki disease and toxic shock syndrome. Prompt recognition and treatment are critical to manage potential life-threatening complications such as myocarditis and coronary artery aneurysm.

Signs and symptoms

The presentation is marked by a persistent high fever and a constellation of symptoms affecting various systems. Common gastrointestinal manifestations include severe abdominal pain, vomiting, and diarrhea, which can mimic conditions like appendicitis. A prominent polymorphous rash, conjunctivitis without exudate, and mucocutaneous changes such as cracked lips or strawberry tongue are frequently observed. Cardiovascular involvement is a major concern, presenting as hypotension, shock, or signs of myocarditis on echocardiography. Neurological symptoms may include headache, lethargy, and meningismus, while other findings can encompass lymphadenopathy and swelling in the hands and feet.

Causes and pathophysiology

The condition is a post-infectious complication, occurring weeks after an acute or often asymptomatic infection with SARS-CoV-2. The precise pathophysiology involves a dysregulated immune response, where viral particles or superantigens trigger an excessive inflammatory cascade. This leads to a marked elevation of inflammatory markers such as C-reactive protein, ferritin, and interleukin-6, resembling a cytokine storm. The immune dysregulation shares mechanistic similarities with Kawasaki disease and macrophage activation syndrome, involving activation of T cells and monocytes. Research from institutions like the National Institutes of Health and Imperial College London continues to investigate the specific antigenic triggers and genetic predispositions.

Diagnosis

Diagnosis is primarily clinical, based on criteria established by the World Health Organization and the Centers for Disease Control and Prevention. Essential criteria include fever, elevated inflammatory markers, evidence of multisystem involvement, and a temporal link to COVID-19, confirmed by PCR testing, serology, or exposure history. Key laboratory findings include significant leukocytosis, neutrophilia, and elevated D-dimer and troponin levels. Echocardiography is mandatory to assess for coronary artery aneurysm and ventricular dysfunction. The diagnostic process requires the exclusion of other infectious causes like bacterial sepsis and non-infectious mimics such as acute appendicitis or inflammatory bowel disease.

Treatment

First-line therapy typically involves immunomodulation with intravenous immunoglobulin and corticosteroids, such as methylprednisolone. For cases refractory to initial treatment or with severe features, biologic agents targeting specific cytokines are employed, including the interleukin-6 receptor antagonist tocilizumab and the tumor necrosis factor inhibitor infliximab. Supportive care in a pediatric intensive care unit is often necessary, involving vasopressor support for shock, management of myocarditis, and anticoagulation therapy to prevent thrombosis. Treatment protocols have been informed by collaborative efforts from organizations like the American College of Rheumatology and experiences from Great Ormond Street Hospital.

Epidemiology

The condition is rare, with most cases reported in regions heavily affected by the COVID-19 pandemic, including the United States, United Kingdom, France, and Italy. Surveillance data from the Centers for Disease Control and Prevention and the European Centre for Disease Prevention and Control indicate a higher incidence among children of Hispanic and Black descent. The median age of affected children is between 6 and 11 years, and it occurs more frequently in males. The incidence appears to have fluctuated with waves of SARS-CoV-2 infection, with variants like Delta and Omicron influencing case numbers.

Prognosis

With timely diagnosis and appropriate immunomodulatory treatment, the majority of children recover fully. However, a significant proportion, especially those with severe cardiovascular involvement, may develop long-term cardiac sequelae. These can include persistent coronary artery aneurysm, ventricular dysfunction, and conduction abnormalities, necessitating long-term follow-up with echocardiography and cardiology. Mortality is low but remains a risk, primarily associated with complications like refractory shock or severe myocarditis. Ongoing cohort studies, such as those led by the National Institutes of Health, aim to understand the long-term outcomes and optimal surveillance strategies for survivors.

Category:Pediatrics Category:Inflammatory disorders Category:COVID-19