A coronary aneurysm caused by KD is a bulging, weakened segment of a coronary artery that can develop weeks after the acute fever phase. While many aneurysms shrink or disappear with proper treatment, larger lesions can persist, increasing the risk of thrombosis, myocardial ischemia, or sudden cardiac death.

Early recognition and aggressive therapy are critical because the heart is the organ most frequently affected by the long‑term complications of Kawasaki disease.

Common Causes

Coronary aneurysms are not exclusive to Kawasaki disease. Below are ten conditions—both infectious and non‑infectious—that can produce coronary artery dilatation. In the context of KD, the primary trigger is an abnormal immune response, but it is useful to know other etiologies for differential diagnosis.

• Untreated or delayed‑treated Kawasaki disease – the most common cause of childhood coronary aneurysms.
• Polyarteritis nodosa – a systemic necrotizing vasculitis that may involve coronary arteries.
Takayasu arteritis – large‑vessel vasculitis that can extend to coronary ostia.
• Infectious arteritis – bacterial (e.g., syphilis, tuberculosis) or viral (e.g., Coxsackie, HIV) infections.
• Connective‑tissue disorders – Marfan syndrome, Ehlers‑Danlos syndrome, and Loeys‑Dietz increase arterial wall fragility.
• Congenital coronary artery anomalies – some infants are born with inherent vessel wall weakness.
• Drug‑induced vasculitis – certain medications (e.g., cocaine, amphetamines) cause vasospasm and subsequent aneurysm formation.
• Behçet disease – a multisystem inflammatory disorder that can involve coronary vessels.
• Systemic lupus erythematosus (SLE) – immune complex deposition may weaken coronary walls.
• Traumatic or iatrogenic injury – coronary catheterization or cardiac surgery can occasionally create pseudo‑aneurysms.

Associated Symptoms

Many children with Kawasaki disease present with classic systemic signs before a coronary aneurysm becomes evident. Once an aneurysm forms, symptoms may be subtle or mimic other cardiac conditions.

• Persistent high fever (>5 days) that does not respond to antibiotics.
• Conjunctival injection (red eyes) without discharge.
• Oral mucosal changes – cracked lips, "strawberry" tongue.
• Swollen, painful hands and feet; later desquamation (peeling) of skin.
• Polymorphous rash, often on the trunk.
• Enlarged cervical lymph nodes.
• Chest pain or discomfort—possible sign of myocardial ischemia.
• Shortness of breath, especially during exertion.
• Palpitations or irregular heartbeats.
• Syncope (fainting) or near‑syncope, indicating compromised coronary flow.

When to See a Doctor

Because coronary aneurysms can remain silent until a serious event occurs, parents and caregivers should seek medical attention promptly if any of the following appear, even if a child has already been diagnosed with Kawasaki disease.

• Fever continues beyond 5–7 days despite treatment.
• New or worsening chest pain, especially if it radiates to the arm, jaw, or back.
• Sudden shortness of breath or difficulty breathing while at rest.
• Palpitations, irregular heartbeat, or a rapid heart rate (tachycardia) not explained by fever.
• Episodes of fainting or feeling light‑headed.
• Swelling of the hands or feet that does not improve.
• Any sign of bleeding or bruising (possible thrombosis within an aneurysm).
• Persistent rash or skin peeling beyond the typical timeline.

Diagnosis

Diagnosing a coronary aneurysm secondary to Kawasaki disease involves a combination of clinical assessment, laboratory testing, and imaging studies.

Clinical Evaluation

• Complete medical history focusing on fever duration, rash, conjunctivitis, oral changes, and extremity swelling.
• Physical examination for coronary murmurs, pericardial friction rubs, and peripheral edema.

Laboratory Tests

• Acute‑phase reactants: Elevated C‑reactive protein (CRP) and erythrocyte sedimentation rate (ESR) indicate ongoing inflammation.
• Complete blood count (CBC): Leukocytosis, normocytic anemia, and thrombocytosis (especially after the first week) are typical.
• Serum albumin: Low levels may predict a higher risk of aneurysm formation.
• Urinalysis: Sterile pyuria can be a clue in KD.

Imaging Studies

• Echocardiography: First‑line, non‑invasive tool performed at diagnosis, 1‑2 weeks, and 6‑8 weeks later. Detects coronary dilation, aneurysm size, and myocardial function.
• Cardiac CT angiography (CTA): Provides high‑resolution images of coronary anatomy; useful when echocardiogram windows are limited.
• Magnetic resonance angiography (MRA): An alternative to CTA without ionizing radiation; helpful for serial follow‑up.
• Coronary catheter angiography: Gold standard for definitive anatomy, reserved for large or symptomatic aneurysms.

Classification of Aneurysm Size

According to the American Heart Association, aneurysms are classified by the internal diameter relative to the adjacent normal segment:

1. Small: < 5 mm or Z‑score < 5.
2. Medium: 5–8 mm or Z‑score 5–10.
3. Large/giant: >8 mm or Z‑score >10.

Treatment Options

Management is two‑fold: control the underlying inflammation and prevent or treat complications* of the aneurysm.