A fine line between macrophage activation syndrome and multisystem inflammatory syndrome in children - literature review based on two case reports

Proteomic Signatures of Multisystem Inflammatory Syndrome in Children (MIS-C) Associated with COVID-19: A Narrative Review

BACKGROUND/OBJECTIVES

Multisystem Inflammatory Syndrome in Children (MIS-C) is a post-infectious complication of COVID-19. MIS-C has overlapping features with other pediatric inflammatory disorders including Kawasaki Disease (KD), Macrophage Activation Syndrome (MAS), Toxic Shock Syndrome and sepsis. The exact mechanisms responsible for the clinical overlap between MIS-C and these conditions remain unclear, and biomarkers that could distinguish MIS-C from its clinical mimics are lacking. This study aimed to provide an overview of how proteomic methods, like Mass Spectrometry (MS) and affinity-based proteomics, can offer a detailed understanding of pathophysiology and aid in the diagnosis and prognosis of MIS-C.

METHODS

A narrative review of relevant studies published up to July 2024 was conducted.

RESULTS

We identified 15 studies and summarized their key proteomic findings. These studies investigated the serum or plasma proteome of MIS-C patients using MS, Proximity Extension, or Aptamer-based assays. The studies associated the proteomic profile of MIS-C with laboratory and clinical parameters and/or compared it with that of other diseases including acute COVID-19, KD, MAS, pediatric rheumatic diseases, sepsis and myocarditis or pericarditis following COVID-19 mRNA immunization. Depending on the method and the control group, different proteins were increased or decreased in the MIS-C group. The limitations and challenges in MIS-C proteomic research are also discussed, and future research recommendations are provided.

CONCLUSIONS

Although proteomics appear to be a promising approach for understanding the pathogenesis and uncovering candidate biomarkers in MIS-C, proteomic studies are still needed to recognize and validate biomarkers that could accurately discriminate MIS-C from its clinical mimics.

Multisystem inflammatory syndrome in children: an evolving understanding of a syndrome amid the inflammatory continuum

Multisystem inflammatory syndrome in children (MIS-C) is a rare hyperinflammatory and immunosuppressed condition affecting children exposed to COVID-19. MIS-C has been associated with an over-exaggerated innate and adaptive immune response characterized by a 'selective' cytokine production and T cell suppression. As COVID-19 information has evolved, the knowledge and field surrounding MIS-C is ever evolving. Thus, a comprehensive clinical review that concisely presents current literature findings regarding common clinical presentations and comparisons with similar conditions, associations with the COVID-19 vaccine effects and relevant epigenetic markers and evaluates treatment and long-term outcomes to help guide future studies is needed and provided.

Case report: Multisystem inflammatory syndrome in children associated with COVID-19, macrophage activation syndrome, and incomplete Kawasaki disease

Background

Multisystem inflammatory syndrome in children (MIS-C), is a severe complication of coronavirus disease 2019 (COVID-19), characterized by persistent fever, systemic inflammatory response, and organ failure. MIS-C with a history of COVID-19 may share clinical features with other well-defined syndromes such as macrophage activation syndrome, Kawasaki disease, hemophagocytic syndrome and toxic shock syndrome.

Case 1

An 11-year-old male with a history of hypothyroidism and precocious puberty with positive antibody test for COVID-19 was admitted for fever, poor general condition, severe respiratory distress, refractory shock, and multiple organ failure. His laboratory examination showed elevated inflammatory parameters, and bone marrow aspirate showed hemophagocytosis.

Case 2

A 13-year-old male with a history of attention deficit hyperactivity disorder and cognitive delay presented clinical manifestations of Kawasaki disease, fever, conjunctival congestion, exanthema, and hyperemia in oral mucosa, tongue, and genitals, with refractory shock and multiple organ failure. Reverse transcriptase polymerase chain reaction (RT-PCR) and antibodies for COVID-19 were negative, inflammation parameters were elevated, and bone marrow aspirate showed hemophagocytosis. Patients required intensive care with invasive mechanical ventilation, vasopressor support, intravenous gamma globulin, systemic corticosteroids, low molecular weight heparin, antibiotics, and monoclonal antibodies and, patient 2 required renal replacement therapy.

Conclusions

Multisystemic inflammatory syndrome in children can have atypical manifestations, and identifying them early is very important for the timely treatment and prognosis of patients.

Mechanisms of Immune Dysregulation in COVID-19 Are Different From SARS and MERS: A Perspective in Context of Kawasaki Disease and MIS-C

Coronaviruses have led to three major outbreaks to date-Severe Acute Respiratory Syndrome (SARS; 2002), Middle East Respiratory Syndrome (MERS; 2012) and the ongoing pandemic, Coronavirus Disease (COVID-19; 2019). Coronavirus infections are usually mild in children. However, a few children with MERS had presented with a severe phenotype in the acute phase resulting in progressive pneumonic changes with increasing oxygen dependency and acute respiratory distress requiring ventilatory support. A subset of children with a history of SARS-CoV-2 infection develops a multisystem hyper-inflammatory phenotype known as Multisystem Inflammatory Syndrome in Children (MIS-C). This syndrome occurs 4-6 weeks after infection with SARS-CoV-2 and has been reported more often from areas with high community transmission. Children with MIS-C present with high fever and often have involvement of cardiovascular, gastrointestinal and hematologic systems leading to multiorgan failure. This is accompanied by elevation of pro-inflammatory cytokines such as IL-6 and IL-10. MIS-C has several similarities with Kawasaki disease (KD) considering children with both conditions present with fever, rash, conjunctival injection, mucosal symptoms and swelling of hands and feet. For reasons that are still not clear, both KD and MIS-C were not reported during the SARS-CoV and MERS-CoV outbreaks. As SARS-CoV-2 differs from SARS-CoV by 19.5% and MERS by 50% in terms of sequence identity, differences in genomic and proteomic profiles may explain the varied disease immunopathology and host responses. Left untreated, MIS-C may lead to severe abdominal pain, ventricular dysfunction and shock. Immunological investigations reveal reduced numbers of follicular B cells, increased numbers of terminally differentiated CD4+T lymphocytes, and decreased IL-17A. There is still ambiguity about the clinical and immunologic risk factors that predispose some children to development of MIS-C while sparing others. Host-pathogen interactions in SARS, MERS and COVID-19 are likely to play a crucial role in the clinical phenotypes that manifest. This narrative review focuses on the immunological basis for development of MIS-C syndrome in the ongoing SARS-CoV-2 pandemic. To the best of our knowledge, these aspects have not been reviewed before.

Clinical characteristics of children with MIS-C fulfilling classification criteria for macrophage activation syndrome

BACKGROUND

Macrophage activation syndrome (MAS) is a potentially life-threatening complication of various inflammatory disorders, including multisystem inflammatory syndrome in children (MIS-C). MIS-C refractory to treatment should raise suspicion of MAS, which can be fatal if a definitive diagnosis is delayed. Unfortunately, there is a lack of data on MAS in children with MIS-C.

OBJECTIVE

Our study aims to analyze the risk factors for the development of MAS in MIS-C, its clinical course and response to treatment, and identify predictive factors for pediatric intensive care.

MATERIAL AND METHODS

We analyzed data from the Polish MIS-C registry of the MultiOrgan Inflammatory Syndromes COVID-19 Related Study. Patients were diagnosed according to the WHO MIS-C definition and treated according to national guidelines (Polish Pediatric Society) based on international consensus. MAS definition was based on 2016 Classification Criteria for Macrophage Activation Syndrome Complicating Systemic Juvenile Idiopathic Arthritis.

RESULTS

Two-hundred and seventy four children met the study inclusion criteria. Fifty-nine patients fulfilled MAS classification criteria, nine of which required admission to the pediatric intensive care unit (PICU). MIS-C patients with MAS were significantly older than patients without MAS (median 11.2 vs. 8.1 years). Multivariable analysis showed that age, symptoms characteristic of atypical Kawasaki disease, and skin erosions were significant factors associated with MAS in MIS-C patients. Analysis of laboratory parameters showed that on admission, MIS-C patients with MAS had significantly lower median lymphocyte and platelet counts, albumin and sodium levels, and higher median levels of C-reactive protein, procalcitonin, ferritin, D-dimers, triglycerides, serum creatinine, urea, and γ-glutamyl transpeptidase, and neutrophil count. Multivariate analysis showed that higher procalcitonin, ferritin, and fibrinogen levels at admission were predictive of MAS. Only elevated troponin level was a factor indicating a requirement of PICU hospitalization for children with MAS. MIS-C patients fulfilling MAS criteria were treated more often with intravenous immunoglobulins and steroids than children without MAS. Children with MAS more often required mechanical ventilation. None of the patients required biological agents.

CONCLUSIONS

The clinical course of MAS in MIS-C seems milder, treatment less aggressive, and the prognosis better than expected based on the current knowledge on MAS complicating other rheumatological diseases.

Immunotherapy of multisystem inflammatory syndrome in children (MIS-C) following COVID-19 through mesenchymal stem cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new type of coronavirus causing coronavirus 2019 (COVID-19) that was first observed in Wuhan, China, in Dec. 2019. An inflammatory immune response targeting children appeared during the pandemic, which was associated with COVID-19 named multisystem inflammatory syndrome in children (MIS-C). Characteristics of MIS-C include the classic inflammation findings, multi-organ dysfunction, and fever as the cardinal feature. Up to now, no specific therapy has been identified for MIS-C. Currently, considerable progress has been obtained in the MIS-C treatment by cell therapy, specially Mesenchymal stem cells (MSCs). Unique properties have been reported for MSCs, such as various resources for purification of cell, high proliferation, self-renewal, non-invasive procedure, tissue regenerator, multidirectional differentiation, and immunosuppression. As indicated by a recent clinical research, MSCs have the ability of reducing disease inflammation and severity in children with MIS-C. In the present review study, the benefits and characteristics of MSCs and exosomes are discussed for treating patients with MIS-C.

Macrophage Activation Syndrome in a Child with Juvenile Idiopathic Arthritis Secondary to SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a pandemic affecting many countries and millions of people. Physicians have encountered some rare and challenging cases related to SARS-CoV-2, a novel virus with still many unknowns. In order to share our experience of a such clinical picture, we present here a child with SARS-CoV-2-induced macrophage activation syndrome in the setting of juvenile idiopathic arthritis.