bubble_chart Overview

Mucocutaneous lymph node syndrome (MCLS), also known as Kawasaki disease, is an acute febrile exanthematous pediatric disease primarily characterized by systemic vasculitis. It was first reported in 1967 by Japanese physician Dr. Tomisaku Kawasaki. Due to the potential for severe cardiovascular complications, this condition has garnered significant attention, with an increasing incidence in recent years. In 1990, Beijing Children's Hospital recorded 67 cases of Kawasaki disease among hospitalized patients with rheumatic diseases, compared to 27 cases of rheumatic fever. Data from 11 hospitals in other provinces showed Kawasaki disease cases were twice as many as rheumatic fever cases. Clearly, Kawasaki disease has replaced rheumatic fever as one of the leading causes of acquired heart disease in children in China. Currently, Kawasaki disease is considered an immune-mediated vasculitis and is temporarily classified under connective tissue disorders.

bubble_chart Epidemiology

This disease can affect both infants and children, but 80–85% of patients are under 5 years old, with the highest incidence occurring in infants aged 6–18 months. Boys are more commonly affected, with a male-to-female ratio of 1.3–1.5:1. There is no distinct seasonal pattern, though some suggest a higher prevalence in summer. By 1990, Japan had reported approximately 100,000 cases of Kawasaki disease, with three epidemics occurring in 1979, 1982, and 1986. During these outbreaks, the incidence among children under 4 years old was 172–194 per 100,000. Although fewer cases have been reported worldwide compared to Japan, the disease has been documented in countries ranging from Sweden, the Netherlands, the United States, Canada, the United Kingdom, and South Korea in the north, to Greece, Australia, and Singapore in the south. In China, the first few cases were reported in 1978 in cities such as Beijing, Shanghai, Hangzhou, Chengdu, and Taiwan. By 1989, the *Journal of Practical Pediatrics* had compiled 220 cases from across the country. A national survey conducted from 1983 to 1986 among major children's hospitals and affiliated medical schools recorded 965 hospitalized cases. A second survey from 1987 to 1991 found the number of hospitalized cases had risen to 1,969, with an increasing trend each year. Among these cases, 78.1% were under 4 years old, with a male-to-female ratio of 1.6:1. In the United States, cases are more prevalent among individuals of Japanese descent. Japan has reported a sibling incidence rate of 1–2%, suggesting a genetic predisposition.

bubble_chart Etiology

The disease cause is not yet clear. This disease exhibits certain epidemic and endemic characteristics, with clinical manifestations such as fever, rash, etc., suggesting an association with infection. It is generally believed that multiple pathogens may be involved, including Epstein-Barr virus, retroviruses, or infections by streptococci and propionibacteria. In 1986, it was reported that the retroviral enzyme activity in the supernatant of peripheral blood stranguria lymphocyte cultures from patients was elevated, indicating that the disease might be caused by a retrovirus. However, most studies have not yielded consistent results. In the past, mycoplasma, rickettsia, and dust mites have also been proposed as pathogens, but none have been confirmed. Some have also considered environmental pollution or chemical allergies as possible causes.

Recent studies indicate that significant immune dysregulation occurs during the acute phase of the disease, playing an important role in the mechanism of disease. During the acute phase, there is an imbalance in peripheral blood T-cell subsets, with an increase in CD4 and a decrease in CD8, leading to an elevated CD4/CD8 ratio. This change is most pronounced at 3–5 weeks of illness and normalizes by 8 weeks. The increased CD4/CD8 ratio places the immune system in an activated state, with CD4 secreting more lymphokines, promoting polyclonal activation, proliferation, and differentiation of B cells into plasma cells, resulting in elevated serum levels of IgM, IgA, IgG, and IgE. Activated T cells secrete high concentrations of interleukins (IL-1, 4, 5, 6), gamma-interferon (IFN-γ), and tumor necrosis factor (TNF). These lymphokines and active mediators can induce endothelial cells to express and produce new antigens; on the other hand, they also promote B cells to secrete autoantibodies, leading to cytotoxic effects on endothelial cells and endothelial cell injury, thereby causing vasculitis. Elevated IL-1, IL-6, and TNF can also induce hepatocytes to synthesize acute-phase reactive proteins, such as C-reactive protein, α1-antitrypsin, and haptoglobin, contributing to the acute fever response in this disease. Patients with this disease exhibit elevated circulating immune complexes (CIC), detectable in 50–70% of cases as early as the first week of illness, peaking at weeks 3–4. The mechanism of CIC in this disease remains unclear, but the absence of immune complex deposition at lesion sites and the increase rather than decrease in serum C3 levels do not align with typical immune complex diseases. The trigger for the aforementioned immune dysregulation remains unknown. Currently, it is widely believed that Kawasaki disease is an immune-mediated systemic vasculitis triggered by multiple infectious pathogens in a susceptible host.

[Pathological Changes]

According to the 1990 summary by the Japanese MCLS Research Committee on 217 fatal cases, the pathological morphology of this disease's vasculitis can be divided into four stages:

Stage I: Approximately 1–2 weeks, characterized by: (1) inflammation of small stirred pulse, small veins, microvessels, and their surroundings; (2) inflammation of medium and large stirred pulse and their surroundings; (3) infiltration of lymphocytes and other white blood cells, along with local edema.

Stage II: Approximately 2–4 weeks, characterized by: (1) reduced inflammation in small vessels; (2) predominant inflammation in medium stirred pulse, often with coronary stirred pulse aneurysms and thrombosis; (3) rare vascular inflammation in large stirred pulse; (4) prominent mononuclear cell infiltration or necrotic changes.

Stage III: Approximately 4–7 weeks, characterized by: (1) subsiding inflammation in small vessels and microvessels; (2) granuloma formation in medium stirred pulse.

Stage IV: Approximately 7 weeks or longer, acute vascular inflammation mostly resolves, replaced by thrombosis, obstruction, intimal thickening leading to stirred pulse aneurysms, and scar formation in medium stirred pulse. Regarding the distribution of stirred pulse lesions, they can be categorized as: (1) extra-organ medium or large stirred pulse, often affecting coronary stirred pulse, axillary, iliac stirred pulse, and other stirred pulse in the neck, chest, and abdomen; (2) intra-organ stirred pulse, involving systemic organs such as the heart, kidneys, lungs, gastrointestinal tract, skin, liver, spleen, gonads, salivary glands, and brain.

In addition to vasculitis, the pathology also involves multiple organs, with interstitial myocarditis, pericarditis, and endocarditis being the most prominent. These can affect the conduction system and often lead to death during stage I lesions. By stages II and IV, ischemic heart disease is commonly observed, and myocardial infarction can be fatal. Additionally, ruptured aneurysms and myocarditis are also significant causes of death in stages II and III.

The vascular pathology of MCLS is very similar to that of infantile polyarteritis nodosa. In addition to coronary artery or pulmonary artery aneurysms and thrombosis, changes are also observed in the vascular intima of the aorta, ileum artery, or pulmonary artery. Fluorescent antibody tests reveal deposits of immunoglobulin IgG in the arterial walls of the heart, spleen, and lymph nodes. Vasculitis may also occur in the cervical lymph nodes and skin, accompanied by fibrinoid necrosis of small blood vessels. Additionally, there is marked thymic atrophy, increased heart weight, hypertrophic dilation of the ventricles, grade I fatty degeneration of the liver, as well as congestion and follicular enlargement in the lymph nodes. However, there are no significant lesions in the glomeruli.

The differences between this disease and classic polyarteritis nodosa (Kussmaul-Maier type) are as follows: (1) The vasculitis in the latter shows prominent fibrinoid necrosis, whereas MCLS rarely exhibits such necrotic changes or only mild changes; (2) Classic polyarteritis nodosa rarely involves the pulmonary arteries.

bubble_chart Clinical Manifestations

Main symptoms

Common persistent fever, lasting 5–11 days or longer (2 weeks to 1 month), with body temperature often reaching above 39°C, unresponsive to antibiotic treatment. Common bilateral conjunctival congestion, reddened lips with rhagades or bleeding, and a Chinese wax myrtle bark-like tongue. Hard edema appears in the hands, with early redness on the palms and soles, followed by characteristic large-scale peeling of the fingertips after 10 days, occurring at the junction of the nail bed and skin. There is also acute non-suppurative transient cervical lymph node swelling, most prominent in the anterior neck, with a diameter of about 1.5 cm or more, mostly unilateral, slightly tender, occurring within 3 days of fever and resolving spontaneously after a few days. Shortly after fever onset (approximately 1–4 days), maculopapular or polymorphous erythema-like rashes appear, occasionally miliaria-like rashes, mostly on the trunk, without vesicles or crusting, resolving in about a week.

Other symptoms

Cardiac damage often occurs, manifesting as symptoms of myocarditis, pericarditis, and endocarditis. The patient's pulse accelerates, and auscultation may reveal tachycardia, gallop rhythm, and muffled heart sounds. Systolic murmurs are also common. Valvular insufficiency and heart failure may occur. Echocardiography and coronary angiography can detect coronary artery aneurysms, pericardial effusion, left ventricular enlargement, and mitral regurgitation in most patients. Chest X-rays may show an enlarged heart shadow. Occasionally, joint pain or swelling, cough, runny nose, abdominal pain, grade I jaundice, or manifestations of aseptic meningoencephalitis may occur.

In the acute phase, about 20% of cases exhibit redness and desquamation of the perineal and perianal skin, with reappearance of erythema or crusting at the site of BCG vaccination 1–3 years prior. During the convalescent stage, transverse grooves of varying lengths may appear on the nails.

The initial stage [first stage] of the disease course is the acute febrile phase, generally lasting 1–11 days, with main symptoms appearing sequentially after fever onset, and severe myocarditis may occur.

The intermediate stage [second stage] is the subacute phase, generally lasting 11–21 days, with most patients experiencing a drop in body temperature and symptom relief, along with membranous peeling of the fingertips. Severe cases may still have persistent fever. Coronary artery aneurysms may lead to myocardial infarction or aneurysm rupture.

Most patients enter the late stage [third stage], or convalescent stage, by the 4th week, generally lasting 21–60 days, with clinical symptoms subsiding. If no significant coronary artery lesions are present, gradual recovery occurs; if coronary artery aneurysms are present, they may continue to develop, leading to myocardial infarction or ischemic heart disease.

A small number of severe coronary artery aneurysm patients enter a chronic phase, which may persist for years, leaving behind coronary artery stenosis, angina pectoris, cardiac insufficiency, or ischemic heart disease, potentially life-threatening due to myocardial infarction.

bubble_chart Auxiliary Examination

During the acute phase, the total white blood cell count and the percentage of granulocytes increase, with a left shift in the nuclear series. More than half of the patients may exhibit grade I anemia. The erythrocyte sedimentation rate (ESR) is significantly accelerated, reaching over 100mm in the first hour. Serum protein electrophoresis shows an increase in globulins, particularly a significant rise in α2-globulin. Albumin levels decrease. IgG, IgA, and IgA levels are elevated. Platelet counts begin to rise in the second week. The blood exhibits a hypercoagulable state. The anti-streptolysin O (ASO) titer is normal. Rheumatoid factor and antinuclear antibodies are both negative. C-reactive protein (CRP) levels are elevated. Blood moistening and tonifying substances are normal or slightly elevated. Urinary sediment may show an increase in white blood cells and/or proteinuria. Electrocardiograms (ECGs) may reveal various abnormalities, with ST-segment and T-wave abnormalities being the most common. Prolonged P-R and Q-T intervals, abnormal Q waves, and arrhythmias may also be observed.

Two-dimensional echocardiography is suitable for cardiac examination and long-term follow-up. In half of the cases, various cardiovascular lesions such as pericardial effusion, left ventricular enlargement, mitral regurgitation, and coronary artery dilation or the formation of coronary artery aneurysms can be detected. It is recommended to perform this examination weekly during the acute and subacute phases of the disease, as it is the most reliable non-invasive method for monitoring coronary artery aneurysms.

In cases of aseptic meningitis, the cerebrospinal fluid may show lymphocyte counts as high as 50–70/mm³. Some cases may exhibit slightly elevated serum bilirubin or alanine aminotransferase (ALT) levels. Bacterial cultures and viral isolation yield negative results.

bubble_chart Diagnosis

The Japanese MCLS Research Committee (1984) proposed that the diagnostic criteria for this disease should meet at least five of the following six main clinical symptoms to be confirmed:

1. Fever of unknown origin, lasting five days or longer;
2. Bilateral conjunctival congestion;
3. Diffuse congestion of the oral and pharyngeal mucosa, red and cracked lips, and a strawberry tongue;
4. In the initial stage [first stage], indurative edema and erythema of the hands and feet, and membranous desquamation of the fingertips during the convalescent phase;
5. Polymorphous exanthema on the trunk without vesicles or crusts;
6. Non-suppurative swelling of cervical lymph nodes, with a diameter of 1.5 cm or larger. However, if coronary artery aneurysms or dilatation are detected by two-dimensional echocardiography or coronary angiography, confirmation can be made with four positive main symptoms.

In recent years, reports of incomplete or atypical cases have increased, accounting for approximately 10–20%. These cases exhibit only 2–3 main symptoms but have typical coronary artery lesions. They mostly occur in infants. The incidence of coronary artery aneurysms is similar between typical and atypical cases. Once Kawasaki disease is suspected, echocardiography should be performed as soon as possible.

bubble_chart Treatment Measures

Acute phase treatment

1. Gamma globulin: Recent studies have confirmed that early intravenous infusion of gamma globulin combined with oral aspirin can reduce the incidence of coronary artery aneurysms in Kawasaki disease. It is essential to administer the medication within 10 days of onset. The dosage is 400 mg/kg of gamma globulin intravenously per day, infused over 2–4 hours for 4 consecutive days, along with oral aspirin at 50–100 mg/kg per day, divided into 3–4 doses, for 4 days. Afterward, the aspirin dose is reduced to 5 mg/kg per day, administered at draught.
2. Aspirin: Early oral aspirin can control the acute inflammatory process and mitigate coronary artery lesions, but no controlled studies have shown that aspirin treatment reduces the incidence of coronary artery aneurysms. The dose is 30–100 mg/kg per day, divided into 3–4 doses. Japanese physicians tend to use lower doses, based on the observation that patients in the acute phase of Kawasaki disease exhibit reduced absorption and increased clearance of aspirin, necessitating higher doses to achieve anti-inflammatory effects. After 14 days, the dose is reduced to 3–5 mg/kg per day, administered at draught in a single dose, to achieve antiplatelet aggregation effects.
3. Corticosteroids: Adrenocorticosteroids have long been considered to have strong anti-inflammatory effects and can alleviate symptoms. However, it was later discovered that corticosteroids can easily lead to thrombosis, hinder the repair of coronary artery lesions, and promote aneurysm formation. Therefore, corticosteroids such as prednisone should not be used alone. Unless severe myocarditis or persistent high fever occurs in severe cases, prednisone and aspirin may be used in combination. Generally, corticosteroids are not used alone to control the early inflammatory response of Kawasaki disease.

Treatment during the convalescent stage

1. Anticoagulation therapy: During the convalescent stage, patients are given aspirin at 3–5 mg/kg per day in a single dose until the erythrocyte sedimentation rate and platelet count return to normal. If no coronary artery abnormalities are present, the medication is usually discontinued 6–8 weeks after onset. Follow-up echocardiography is performed at 6 months and 1 year. Patients with chronic coronary artery lesions require long-term anticoagulation therapy and close follow-up. Those with small single coronary artery aneurysms should take aspirin at 3–5 mg/kg per day until the aneurysm resolves. For patients intolerant to aspirin, dipyridamole may be used at 3–6 mg/kg per day, divided into 2–3 doses. Annual cardiac evaluations are necessary. If echocardiography, clinical data, or exercise tests suggest myocardial ischemia, coronary angiography should be performed. Patients with multiple or large coronary aneurysms should take aspirin and dipyridamole long-term. Patients with giant aneurysms are prone to thrombosis, coronary artery stenosis, or occlusion and may require oral warfarin anticoagulation. These patients should limit physical activity and avoid sports. Cardiac evaluations should be performed every 3–6 months. If myocardial ischemia is evident or exercise tests are positive, coronary angiography should be performed to assess the progression of stenosis. Patients with occlusion of one or more major coronary arteries should receive long-term anticoagulation therapy, undergo repeated cardiac evaluations (including myocardial scans, exercise tests, and coronary angiography), and consider surgical treatment.
2. Thrombolytic therapy: For patients with myocardial infarction and thrombosis, intravenous or catheter-based percutaneous coronary artery administration is used to promote coronary recanalization and myocardial reperfusion. Intravenous thrombolysis involves administering 20,000 units/kg of urokinase within 1 hour, followed by 3,000–4,000 units/kg per hour. For coronary artery administration, 1,000 units/kg of urokinase is given within 1 hour. Streptokinase may also be used, with 10,000 units/kg administered intravenously within 1 hour, and another dose given after 30 minutes. These drugs rapidly dissolve fibrin, are highly effective, and have no adverse effects.
3. Coronary angioplasty: In recent years, balloon catheters have been successfully used to dilate stenotic coronary arteries.
4. Surgical treatment: The indications for coronary artery bypass grafting are: (1) high-grade occlusion of the left main coronary artery; (2) high-grade occlusion of multiple branches; (3) high-grade occlusion of the proximal left anterior descending artery. For cases of severe mitral regurgitation that are unresponsive to medical therapy, mitral valve repair or mitral valve replacement can be performed. A Japanese study reported 62 Kawasaki disease patients who underwent coronary artery bypass grafting, among whom 7 also underwent mitral valve surgery. Preoperatively, 70% of the patients had angina pectoris, heart failure, or other symptoms. The 4-year survival rate postoperatively was 87%, and the 10-year survival rate was 45%, with most deaths attributed to late-stage [third-stage] myocardial infarction or sudden death.

In cases of cardiogenic shock, heart failure, and arrhythmias, appropriate treatment should be administered.

bubble_chart Prognosis

The vast majority of children have a good prognosis, with a self-limiting course, and gradual recovery can be achieved with appropriate treatment. This differs significantly from infantile polyarteritis nodosa. However, 15–30% of Kawasaki disease patients may develop coronary artery aneurysms. Death due to coronary artery aneurysms, thrombotic occlusion, or myocarditis accounts for 1–2% of all cases, and sudden death can even occur during the convalescent stage. Post-ischemic heart disease is very rare. Recurrence occurs in about 2% of cases. The mortality rate has recently declined to 0.5–1.0%. An analysis of 104 Kawasaki disease deaths in Japan showed that 57% were due to myocardial infarction, 12% to heart failure, 6.7% to myocardial infarction combined with heart failure, 5% to coronary artery aneurysm rupture, and 1% to arrhythmia, with other causes including concurrent infections. Since 1986, Beijing Children's Hospital has examined 188 Kawasaki disease cases using two-dimensional echocardiography, detecting coronary artery lesions in 60 cases, including 44 cases of dilation and 16 cases of aneurysm formation. Follow-up ranged from 3 months to 5 years, with an average of 22.6 months. Among them, 40 cases of dilation and 6 cases of aneurysm returned to normal, with recovery times of 4.4 ± 2.9 months and 15.7 ± 17.2 months, respectively. Two deaths occurred: one case involved multiple grade II coronary artery aneurysms (internal diameter 7 mm) due to acute anterior wall myocardial infarction, and the other involved multiple giant aneurysms, with rupture of the right coronary artery occurring on day 28 of the disease course.

bubble_chart Complications

Due to the lesions of the coronary arteries, which are both symptoms of the disease itself and potentially fatal complications, this section will detail their progression to facilitate early detection and timely appropriate treatment.

1. Coronary artery lesions: According to observations of 1,009 cases of Kawasaki disease in Japan, transient coronary artery dilation accounted for 46%, and coronary artery aneurysms accounted for 21%. Two-dimensional echocardiography revealed that coronary artery dilation could appear as early as the third day of illness, with most cases resolving within 3–6 months. Coronary artery aneurysms could be detected by the sixth day of illness, with the highest detection rate occurring in the second to third weeks. New lesions rarely appeared after the fourth week. The incidence of coronary artery aneurysms was 15–30%, and the presence of clinical myocarditis did not predict coronary artery involvement. Some well-established risk factors associated with coronary artery aneurysms included age of onset under 1 year, male gender, persistent fever lasting more than 14 days, anemia, total white blood cell count above 30×10⁹/L, erythrocyte sedimentation rate exceeding 100 mm/h, significantly elevated C-reactive protein, decreased plasma albumin, and the presence of peripheral artery aneurysms. Most coronary artery aneurysms followed a self-limiting course, with the majority resolving spontaneously within 1–2 years.
   In this disease, coronary artery lesions most commonly affected the proximal main trunk and the left anterior descending branch, followed by the left circumflex branch, which was less common. Isolated distal artery aneurysms were rare. The severity of coronary artery lesions is generally classified into four grades:
   1. Normal (Grade 0): No dilation of the coronary arteries.
   2. Grade I: Localized aneurysmal dilation with an internal diameter <4 mm.
   3. Grade II: Single, multiple, or extensive aneurysms with an internal diameter of 4–7 mm.
   4. Grade III: Giant aneurysms with an internal diameter ≥8 mm, often extensive and involving more than one branch. The incidence was approximately 5%, with a poor prognosis.
   Therefore, patients with coronary artery lesions should undergo close follow-up and regular echocardiographic examinations. Typically, examinations should be performed weekly within the first 4 weeks of illness, then at 2 months and 6 months, followed by at least annual examinations based on the severity of the lesions. Coronary angiography should be performed for symptomatic patients and those with severe coronary artery involvement. Angiography can accurately assess the degree of coronary artery stenosis, occlusion, and distal lesions. Due to the potential for transient myocardial ischemia, ventricular fibrillation, and other serious complications caused by distal occlusion, coronary angiography is indicated under the following circumstances:
   1. Symptoms of myocardial ischemia.
   2. Persistent cardiac valvular lesions.
   3. Plain X-ray showing coronary artery calcification.
   4. Echocardiography revealing persistent coronary artery aneurysms.
2. Gallbladder hydrops: Most commonly occurring in the subacute phase, it may present with severe abdominal pain, abdominal distension and fullness, and jaundice. A mass may be palpable in the right upper abdomen, and abdominal ultrasound can confirm the diagnosis. Most cases resolve spontaneously, though paralytic ileus or intestinal bleeding may rarely occur.
3. Arthritis or arthralgia: Occurs during the acute or subacute phase, affecting both large and small joints in approximately 20% of cases, resolving as the condition improves.
4. Changes in the nervous system: The acute phase includes aseptic meningoencephalitis, facial nerve palsy, hearing loss, acute encephalopathy, and febrile seizures, which are caused by vasculitis. These are clinically common, recover quickly, and have a good prognosis. Among them, aseptic meningoencephalitis is the most frequent, with an incidence of about 25%. It mostly occurs within the first 2 weeks of the illness. Some children experience increased intracranial pressure, manifesting as bulging fontanelles. A few children exhibit neck stiffness and may have drowsiness, fixed gaze, unconsciousness, or other consciousness disturbances. Cerebrospinal fluid shows grade I lymphocytosis, with normal glucose and chloride levels, and protein levels are mostly normal. Clinical symptoms usually resolve within a few days. Facial nerve palsy is more common in severe cases, often presenting as peripheral palsy, possibly due to vasculitic reactions affecting the facial nerve or adjacent vascular lesions, such as aneurysm formation or arterial dilation, leading to transient compression of the facial nerve. During the convalescence stage, limb paralysis caused by stenosis or occlusion of the middle cerebral artery may result in sequelae, though this is relatively rare.
5. Other complications: Pulmonary vasculitis may show increased lung markings or patchy shadows on chest X-rays, with occasional pulmonary infarction. During the acute phase, urethritis may occur, and urine sediment may reveal increased white blood cells and grade I proteinuria. Iridocyclitis is relatively rare. Approximately 2% of patients develop aneurysms, most commonly in the axillary and iliac arteries. Digital gangrene is occasionally observed.

bubble_chart Differentiation

It should be differentiated from various eruptive pestilential diseases, viral infections, acute lymphadenitis, Bi disease, and other connective tissue diseases, viral myocarditis, wind-dampness carditis, etc.

The differences between this disease and scarlet fever are:

1. The rash begins on the third day after onset;
2. The rash morphology resembles measles and erythema multiforme;
3. The susceptible age is infants and young children;
4. Penicillin is ineffective.

The differences between this disease and juvenile Bi disease are:

1. The fever period is shorter, and the rash is more transient;
2. Hard swelling of hands and feet, often showing metatarsal flushing;
3. Rheumatoid factor is negative.

The differences from exudative erythema multiforme are:

1. No purulent secretions or pseudomembrane formation in the eyes and lips;
2. The rash does not include blisters and crusts.

The differences from systemic lupus erythematosus are:

1. The rash is not prominent on the face;
2. Total white blood cells and platelets are generally elevated;
3. Antinuclear antibodies are negative.
4. The susceptible age is infants and young children, with boys more commonly affected.

There are many similarities with infantile nodular poly stirred pulse syndrome, but MCLS has a higher incidence, shorter course, and better prognosis. The relationship between these two diseases remains to be studied.

The differences from eruptive sexually transmitted viral infections are:

1. Lip flushing, cracking, bleeding, and Chinese wax myrtle bark tongue;
2. Hard swelling of hands and feet, often metatarsal flushing and late-stage [third stage] membranous desquamation of fingertips and toes;
3. No edema or secretions in the conjunctival membrane;
4. Total white blood cells and granulocyte percentage are both elevated, with a left shift;
5. ESR and C-reactive protein are significantly elevated.

The differences from acute lymphadenitis are:

1. Cervical lymph node swelling and tenderness are milder, with no redness or swelling of the local skin and subcutaneous tissue;
2. No suppurative lesions.

The differences from viral myocarditis are:

Coronary stirred pulse lesions are prominent;

Characteristic changes in hands and feet;

Persistent high fever. The differences from wind-dampness carditis are:

1. Coronary stirred pulse lesions are prominent;
2. No significant heart murmurs;
3. The affected age group is mainly infants and young children.