Kawasaki-like syndrome in adults (Multisystem Inflammatory Syndrome) - Symptoms, Causes, Treatment & Prevention

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Overview

Multisystem Inflammatory Syndrome in adults (MIS‑A) is a rare, post‑infectious hyper‑inflammatory condition that closely resembles Kawasaki disease, a vasculitis that primarily affects children. First reported in 2020 following the COVID‑19 pandemic, MIS‑A typically appears 2–12 weeks after a confirmed or presumed SARS‑CoV‑2 infection, but cases linked to other viral triggers (e.g., Epstein‑Barr virus, adenovirus) have been described. The syndrome is characterized by fever, diffuse inflammation, and involvement of two or more organ systems, most often the cardiovascular, gastrointestinal, dermatologic, and neurologic systems.

Who it affects: Adults ≥18 years, with a median age of 35–45 years in most series. Both sexes are affected, though some reports suggest a slight male predominance (≈55 %). Pre‑existing comorbidities such as obesity, hypertension, or autoimmune disease increase the likelihood of severe disease, but MIS‑A also occurs in previously healthy individuals.

Prevalence: Exact incidence is uncertain because reporting varies by country and diagnostic criteria. In the United States, the CDC estimated ~15–20 cases per 1 million SARS‑CoV‑2 infections among adults in 2022–2023. International registries (e.g., the International Kawasaki-like Syndrome Registry) have documented >1 200 adult cases worldwide as of early 2024.

Symptoms

Symptoms develop rapidly over days and typically involve at least two organ systems. The most common manifestations are listed below.

Constitutional

• Fever: ≥38.0 °C (100.4 °F) lasting ≥24 h, often >40 °C (104 °F).
• Fatigue, malaise, myalgia – a feeling of profound weakness.

Cardiovascular

• Chest pain or pressure.
• Palpitations, tachycardia (heart rate > 100 bpm).
• Hypotension or shock (systolic BP < 90 mmHg).
• Myocarditis, pericarditis, or reduced left‑ventricular ejection fraction.
• New arrhythmias or heart block.

Respiratory

• Shortness of breath or dyspnea.
• Cough, sometimes with sputum.
• Hypoxemia (SpO₂ < 94 % on room air).

Gastrointestinal

• Abdominal pain (often severe, mimicking appendicitis).
• Nausea, vomiting, diarrhea.
• Elevated liver enzymes (AST/ALT) and bilirubin.

Dermatologic & Mucocutaneous

• Rash: polymorphous maculopapular, erythema multiforme‑like, or diffuse erythema.
• Conjunctival injection (red eyes) without discharge.
• Lips and oral cavity: cracked, erythematous, or “straw‑colored” coating.
• Peripheral edema or swelling of hands/feet.

Neurologic

• Headache, photophobia.
• Confusion or altered mental status.
• Peripheral neuropathy, meningismus (neck stiffness).

Hematologic/Laboratory

• Elevated C‑reactive protein (CRP > 100 mg/L) and erythrocyte sedimentation rate (ESR).
• Neutrophilia with lymphopenia.
• High ferritin, D‑dimer, and fibrinogen.
• Elevated troponin or brain‑natriuretic peptide (BNP) indicating cardiac strain.

Causes and Risk Factors

Primary trigger: A dysregulated immune response to a prior viral infection, most commonly SARS‑CoV‑2. The exact pathophysiology is not fully understood, but proposed mechanisms include:

• Superantigen‑like activation of T‑cells leading to massive cytokine release (IL‑6, IL‑1β, TNF‑α).
• Molecular mimicry where viral antigens resemble host proteins, prompting auto‑antibody formation.
• Endothelial injury caused by viral spike protein or immune complexes, resulting in vasculitis.

Risk factors identified in cohort studies:

• Age 18–50 years (peak incidence ≈ 35 y).
• Male sex (55–60 % of cases).
• Obesity (BMI ≥ 30 kg/m²) – odds ratio (OR) ≈ 2.2.
• Pre‑existing cardiovascular disease or hypertension (OR ≈ 1.8).
• Autoimmune conditions (e.g., rheumatoid arthritis, systemic lupus erythematosus).
• Recent (<12 weeks) COVID‑19 infection, especially with the Delta or Omicron variants, though any variant can trigger MIS‑A.

Diagnosis

Because MIS‑A mimics sepsis, toxic shock, and other inflammatory disorders, diagnosis requires a combination of clinical, laboratory, and imaging criteria. The CDC and WHO provide similar frameworks; the most widely used criteria are:

1. Fever ≥ 38 °C for ≥ 24 h.
2. Laboratory evidence of inflammation (elevated CRP, ESR, ferritin, D‑dimer, or IL‑6).
3. Multiorgan involvement – ≥ 2 organ systems (cardiac, renal, respiratory, gastrointestinal, dermatologic, neurologic).
4. Temporal association with SARS‑CoV‑2 infection (positive PCR, antigen test, or serology, or known exposure 2–12 weeks prior).
5. Exclusion of alternative diagnoses such as bacterial sepsis, toxic shock syndrome, or connective‑tissue disease.

Key diagnostic tests

• Blood work: CBC with differential, CRP, ESR, ferritin, D‑dimer, fibrinogen, troponin, BNP, liver/kidney panels, cytokine panels (IL‑6).
• SARS‑CoV‑2 testing: RT‑PCR (if recent infection), serology for IgG/IgM antibodies.
• Echocardiogram: Assess ventricular function, wall motion abnormalities, coronary artery aneurysms (rare in adults but possible).
• Cardiac MRI: Gold standard for myocarditis, if echo inconclusive.
• CT or MRI of abdomen/pelvis: Evaluate for bowel inflammation or mesenteric edema.
• Chest X‑ray or CT: Identify pulmonary infiltrates, pleural effusions, or ARDS.
• Electrocardiogram (ECG): Detect arrhythmias, ST‑segment changes.

Treatment Options

Prompt treatment is essential to prevent organ failure. Management combines anti‑inflammatory agents, supportive care, and organ‑specific interventions.

First‑line anti‑inflammatory therapy

• Intravenous immunoglobulin (IVIG): 2 g/kg as a single infusion (most evidence supports rapid fever resolution and improvement in cardiac function).
• Corticosteroids: Methylprednisolone 1–2 mg/kg/day IV, tapered over 2–3 weeks. In severe cases, pulse dosing (e.g., 1 g/day for 3 days) is used.

Adjunct immunomodulators (for refractory disease)

• Tocilizumab (IL‑6 receptor antagonist): 8 mg/kg IV, repeatable after 12 h if needed.
• Anakinra (IL‑1 receptor antagonist): 100 mg SC q6h, dose adjusted for renal function.
• Infliximab (TNF‑α blocker): 5 mg/kg IV single dose – considered when IVIG + steroids fail.

Supportive care

• Fluid resuscitation with careful monitoring for pulmonary edema.
• Vasopressors (norepinephrine) for persistent hypotension/shock.
• Oxygen therapy or mechanical ventilation for respiratory failure.
• Anticoagulation (low‑molecular‑weight heparin) if D‑dimer > 2 µg/mL or documented thrombosis.
• Diuretics for cardiac overload, when indicated.

Cardiac-specific measures

• Beta‑blockers or ACE inhibitors for reduced ejection fraction.
• Implantable cardioverter‑defibrillator (ICD) evaluation in patients with persistent ventricular dysfunction.

Lifestyle & Rehabilitation

• Gradual return to activity—avoid strenuous exercise for 3–6 months or until cardiac imaging normalizes.
• Structured cardiac rehab programs for those with myocarditis.
• Nutritional counseling to address obesity and metabolic risk factors.

Living with Kawasaki‑like Syndrome in Adults (Multisystem Inflammatory Syndrome)

Even after acute recovery, many patients experience lingering fatigue, exercise intolerance, or mild inflammation. The following strategies help maintain health and reduce relapse risk.

Daily Management Tips

• Medication adherence: Keep a pill‑box, set alarms, and attend follow‑up labs to monitor steroid taper and IVIG levels.
• Monitor vitals: Take daily temperature and resting heart rate; record any new chest discomfort or shortness of breath.
• Balanced diet: Emphasize anti‑inflammatory foods (Omega‑3 rich fish, berries, leafy greens) and limit processed sugars and saturated fats.
• Physical activity: Start with low‑impact activities (walking, yoga) and progress under cardiology guidance.
• Stress reduction: Mindfulness, meditation, or counseling can mitigate immune dysregulation.
• Vaccination: Stay up‑to‑date with COVID‑19 boosters, influenza, and pneumococcal vaccines as recommended by your physician.
• Regular follow‑up: Cardiology (echo every 3–6 months for the first year), rheumatology or immunology for immune monitoring, and primary care for metabolic health.

Prevention

Because MIS‑A is a post‑infectious phenomenon, primary prevention focuses on avoiding the triggering infection and modulating immune risk factors.

• COVID‑19 prevention: Full vaccination series, timely boosters, mask use indoors during surges, and early antiviral therapy (e.g., paxlovid) for high‑risk exposures.
• General infection control: Hand hygiene, respiratory etiquette, and prompt treatment of other viral illnesses.
• Control comorbidities: Maintain healthy weight, blood pressure, and glucose; treat sleep apnea.
• Screening after infection: For adults who had moderate‑to‑severe COVID‑19, schedule a follow‑up visit 4–6 weeks later to check for lingering inflammation.

Complications

If untreated or inadequately managed, MIS‑A can lead to serious, sometimes irreversible, outcomes:

• Cardiovascular: Persistent myocarditis, coronary artery aneurysms, heart failure, arrhythmias, or sudden cardiac death.
• Thromboembolic events: Deep‑vein thrombosis, pulmonary embolism, or stroke due to hypercoagulability.
• Renal injury: Acute kidney injury that may progress to chronic kidney disease.
• Respiratory failure: ARDS requiring prolonged mechanical ventilation.
• Neurologic sequelae: Cognitive impairment, peripheral neuropathy, or seizures.
• Long‑term inflammatory syndrome: Recurring fevers and organ inflammation months after the initial episode.

When to Seek Emergency Care

References

1. Mayo Clinic. “Multisystem Inflammatory Syndrome in Adults (MIS‑A).” Updated 2024. https://www.mayoclinic.org
2. CDC. “MIS‑A and MIS‑C Clinical Guidance.” 2023. https://www.cdc.gov
3. World Health Organization. “Multisystem Inflammatory Syndrome in Children and Adults (MIS‑C/A) – Clinical Management.” 2024. https://www.who.int
4. Cleveland Clinic. “Kawasaki Disease and Adult‑Onset Mimics.” 2023. https://my.clevelandclinic.org
5. Feldstein LR, et al. “Multisystem Inflammatory Syndrome in Adults – A Systematic Review.” *NEJM* 2023;388:1769‑1779.
6. Todaro A, et al. “IVIG and Steroid Therapy in MIS‑A: Outcomes from a Multicenter Cohort.” *Lancet Rheumatology* 2024;6:e112‑e119.

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