Kawasaki disease and coronary complications — formative SAQs

SAQ 1 (10 marks)

A two-year-old boy is brought to the emergency department with fever for six days, bilateral red eyes without discharge, cracked and bleeding lips, a strawberry tongue, a widespread maculopapular rash, and swollen red palms and soles. His C-reactive protein is 96 mg/L and his platelet count is 520 000 per microlitre. He has had no echocardiogram yet. [1]

1. State the diagnostic criteria for complete Kawasaki disease and explain how you would manage incomplete disease, including the supplementary laboratory criteria. (3) [1]
2. Give the standard acute treatment regimen, the timing that maximises coronary protection, and the evidence that underpins it. (4) [1] [2]
3. Describe how you would reassess the child after treatment, define IVIG-resistant disease, and outline its management. (3) [1] [3]

Model answer — SAQ 1

(1) Diagnostic criteria and incomplete disease (3). Complete Kawasaki disease is fever for five days or more plus four or five of the five principal features: bilateral non-purulent conjunctivitis, oral changes (red cracked lips, strawberry tongue, oropharyngeal erythema), polymorphous rash, extremity changes (acute erythema and oedema of palms and soles, later peeling), and cervical lymphadenopathy of at least 1.5 centimetres. In incomplete disease — fever with two or three features, commonest under six months and in older children — I treat on clinical suspicion using supportive evidence: an abnormal echocardiogram, or a raised CRP or ESR plus three or more supplementary laboratory criteria (anaemia for age, platelets over 450 000 per microlitre after day seven, albumin under 35 g/L, raised alanine aminotransferase, white cells over 15 000, and sterile pyuria). The coronary risk is at least as high in incomplete disease, so I do not wait for the full criteria. [1]

(2) Standard treatment and its evidence (4). The standard regimen is a single infusion of intravenous immunoglobulin at 2 g/kg over ten to twelve hours together with high-dose aspirin at 30 to 50 mg/kg per day in divided doses, given as early as possible and ideally within ten days of fever onset. When the child is afebrile the aspirin steps down to an anti-thrombotic dose of 3 to 5 mg/kg per day and continues until the coronaries are normal at six to eight weeks. The evidence is the landmark 1986 trial showing that IVIG plus aspirin reduced coronary aneurysms from about a quarter to under five per cent, and the 1991 trial establishing that a single 2 g/kg infusion was superior to four smaller infusions. Treating within ten days is the single biggest modifiable factor preventing aneurysms. [1] [2]

(3) Reassessment and IVIG resistance (3). I reassess at 36 to 48 hours after IVIG: resolution of fever suggests a responsive course, while persistent or recrudescent fever defines IVIG-resistant disease, which affects about fifteen per cent of children and marks the group at highest coronary risk. For resistance I escalate to infliximab at 5 to 10 mg/kg or a second IVIG at 2 g/kg; the KIDCARE randomised trial showed infliximab shortened fever duration and length of stay with a comparable coronary outcome. I repeat the echocardiogram and trend the inflammatory markers, and I arrange onward escalation to corticosteroids or other adjuncts for multi-refractory disease. [1] [3]

SAQ 2 (10 marks)

A 19-year-old man with a history of Kawasaki disease at age three, complicated by a giant coronary artery aneurysm of the right coronary artery, presents to the emergency department with exertional central chest pain and one episode of syncope. An electrocardiogram shows anterior T-wave inversion, and his high-sensitivity troponin is elevated. [5] [6]

1. Interpret the presentation and explain why Kawasaki disease is relevant to his acute coronary syndrome, including the mechanism of late coronary events. (3) [5] [6]
2. Describe the immediate and definitive management of his acute coronary event, and how it differs from a typical adult atherosclerctic infarct. (4) [5]
3. Outline the principles of his long-term coronary surveillance and anti-thrombotic management after this event. (3) [1] [6]

Model answer — SAQ 2

(1) Interpretation and mechanism (3). This young man has acute myocardial ischaemia or infarction on the background of a giant right coronary aneurysm from childhood Kawasaki disease, and Kawasaki disease is a leading cause of myocardial infarction in young adults with a childhood cardiac history. The mechanism is that giant aneurysms destroy the internal elastic lamina and medial layer; over years they may persist and progress to stenotic lesions or develop thrombus, producing ischaemia or infarction decades after the acute illness. His exertional chest pain with syncope, anterior T-wave inversion and a raised troponin are ischaemia until proven otherwise. [5] [6]

(2) Acute and definitive management (4). Immediate management follows the acute coronary syndrome pathway: anti-platelet therapy with aspirin, a second anti-platelet agent, anticoagulation, analgesia, and urgent cardiology involvement with transfer to a cardiac centre. The key difference from a typical adult atherosclerctic infarct is the underlying anatomy — he has aneurysmal and likely stenotic or thrombotic coronary disease rather than an atherosclerctic plaque rupture — so definitive management is coronary angiography defining the aneurysm, stenosis and thrombus, with thrombolysis, percutaneous intervention or bypass grafting individualised to the anatomy. His anticoagulation and anti-platelet intensity must account for the high thrombotic risk of the giant aneurysm. [5]

(3) Long-term surveillance and anti-thrombotic management (3). After the event he enters intensive lifelong surveillance with serial echocardiography, exercise testing and coronary imaging (computed tomography or magnetic resonance angiography) to detect stenosis, thrombus and left-ventricular function. Anti-thrombotic therapy combines anti-platelet agents with anticoagulation given the giant aneurysm, with intensity matched to the persistent thrombotic risk. He needs a structured transition into adult cardiac and adult congenital care with a clear plan for recurrent symptoms, because the risk of further ischaemic events persists for life. [1] [6]