Kawasaki disease overview

# Overview
Kawasaki disease, also known as lymph node syndrome, mucocutaneous node disease, infantile polyarteritis and Kawasaki syndrome, is a poorly understood self-limited vasculitis that affects many organs, including the skin, mucous membranes, lymph nodes, blood vessel walls, and the heart. There is no evidence that Kawasaki disease is contagious. It was first described in 1967 by Dr. Tomisaku Kawasaki in Japan.  Kawasaki disease is predominantly a disease of young children, with 80% of patients younger than 5 years of age. Additional risk factors in the United States include Asian race and male sex.  Kawasaki disease can cause vasculitic changes (inflammation of blood vessels) in the coronary arteries and subsequent coronary artery aneurysms.  Common symptoms of Kawasaki disease include high grade fever, red eyes, bright red and cracked lips,
red mucous membranes in the mouth, strawberry tongue, white coating on the tongue or prominent red bumps (papillae) on the back of the tongue, red palms of the hands and soles of the feet, swollen hands and feet, and rash.  Intravenous immunoglobulin
(IVIG) and aspirin are indicated in Kawasaki disease.

# Historical perspective
Kawasaki disease was first discovered by Dr. Tomisaku Kawasaki when he saw his first case of Kawasaki disease in Japan, in 1961. Later in 1967, Kawasaki published his first report on Kawasaki disease in Japanese. Dr Kawasaki also developed "Japan Kawasaki Disease Research Center" in 1990.

# Classification
Patients whose illness does not meet the diagnostic criteria of Kawasaki disease, but who have fever and coronary artery abnormalities are classified as atypical or incomplete Kawasaki disease. For patients of atypical or incomplete Kawasaki disease, an evidence of coronary abnormalities or CAAs must be shown on the echocardiogram.

# Pathophysiology
The exact pathogenesis of Kawasaki disease is not fully understood. However, it is thought that Kawasaki disease is caused by either environmental, viral,  or genetic causes.  Kawasaki disease is defined as the systemic inflammation of the medium sized arteries and in multiple organs and tissues, which can lead to the associated conditions of hepatitis, interstitial pneumonitis, abdominal pain, vomiting, diarrhea, gallbladder hydrops, aseptic meningitis, irritability, myocarditis, pericarditis, valvulitis, pyuria, pancreatitis, and lymphadenopathy. On gross pathology, large or giant coronary artery aneurysms, thrombi containing aneurysms, decreases in luminal diameter, stenosis of the lumen and chronic inflamation are can be seen.  On microscopic histopathological analysis of autopsied cases of Kawasaki disease, intracytoplasmic inclusion bodies are frequently observed in ciliated bronchial epithelial cells.

# Causes
The exact cause of Kawasaki disease has not been identified. The current etiological theories center primarily on immunological causes for the disease, much research is being carried out to discover a definitive toxin or antigenic substance, possibly a superantigen, that is the specific cause of the disease. There are several hypothesis for the cause of Kawasaki disease, infectious agents thought to induce Kawasaki disease include, parvovirus B19, meningococcal septicemia, adenovirus, bacterial toxinmediated, superantigens, cytomegalovirus, Epstein-Barr virus, human lymphotropic virus, klebsiella pneumoniae bacteremia, mycoplasma pneumoniae, mite-associated bacteria, measles, propionibacterium acnes, parainfluenza type 3 virus, rotavirus infection, rickettsia species and tick-borne diseases.

# Differentiating Kawasaki disease from other diseases
Kawasaki disease must be differentiated from other diseases that cause different rash-like conditions and can be confused with Kawasaki disease. The various conditions that should be differentiated from Kawasaki disease include; infantile polyarteritis nodosa, juvenile idiopathic arthritis, leptospirosis, lyme disease, measles, mercury toxicity, pediatric rocky mountain spotted fever, toxic epidermal necrolysis, staphylococcal scalded skin syndrome, rheumatic fever, impetigo, insect bites, monkey pox, rubella, atypical measles, coxsackie virus, acne, syphilis, molluscum contagiosum, toxic erythema, rat-bite fever, parvovirus B19, cytomegalovirus, scarlet fever, Stevens-Johnson syndrome, varicella-zoster virus, chicken pox, meningococcemia, rickettsial pox, meningitis, toxic shock syndrome, roseola infantum (exanthem subitum), erythema infectiosum (fifth disease), enterovirus, dengue fever, drug - induced rash, infectious mononucleosis, pharyngoconjunctival fever, herpangina, and primary herpetic gingivostomatitis.

# Epidemiology and Demographics
Kawasaki disease (KD) occurs worldwide, with the highest incidence in Japan, and it most often affects boys and younger children. KD may have a winter-spring seasonality, and community-wide outbreaks have been reported occasionally. In the continental United States, population-based and hospitalization studies have estimated an incidence of KD ranging from 9 to 19 per 100,000 children younger than 5 years of age. Approximately 4248 hospitalizations for Kawasaki disease, of which 3277 (77%) were for children under 5 years of age, were estimated among children younger than 18 years of age in the United States in the year 2000.

# Risk factors
Common risk factors in the development of Kawasaki disease are due to a combination of non-modifiable and modifiable risk factors, that include environmental, genetic, and viral factors.

# Screening
There is insufficient evidence to recommend routine screening for Kawasaki disease.

# Natural History, Complications, and Prognosis
If left untreated, the symptoms will eventually relent, but coronary artery aneurysms will not improve, resulting in a significant risk of death or disability due to myocardial infarction.  If treated in a timely fashion, this risk can be mostly avoided and the course of illness cut short. Patients with Kawasaki disease may progress to develop long term cardiovascular illness such as coronary artery disease, and pre-mature atherosclerosis. Common complications of Kawasaki disease include vasculitis and coronary artery aneurysms. Prognosis is generally excellent and the mortality rate of patients with Kawasaki disease is approximately 2%.

# Diagnostic Criteria
Kawasaki disease is diagnosed clinically (by medical signs and symptoms), and there are no specific laboratory tests that can tell if someone has Kawasaki disease. It is normally difficult to establish the diagnosis, especially early in the course of illness, and frequently children are not diagnosed until they have seen a physician several times. Many other serious illnesses can cause similar symptoms, and must be considered in the differential diagnosis, including scarlet fever, toxic shock syndrome, and juvenile idiopathic arthritis. Classically, five days of fever plus four of five diagnostic criteria must be met in order to establish the diagnosis, and include, mucositis (erythema of the palatine mucosa), fissured erythematous lips, "strawberry tongue", rash (polymorphus, usually urticarial erythematous rash mainly in external extremities. The rash can spread to trunk), extremities changes (edema of hands and feet, erythema of palms & soles, desquamation of fingertips, bilateral non-exudative conjuctival erythema), and cervical lymphadenopathy of at least 15 milimeters.

# History and Symptoms
Kawasaki disease often begins with a high and persistent fever that is not very responsive to normal doses of acetaminophen or ibuprofen. The fever may persist and rise steadily for up to two weeks and is normally accompanied by irritability. Affected children develop red eyes, mucous membranes, and lips, a "strawberry tongue", iritis, keratic precipitates (detectable by an ophthalmologist but usually too small to be seen by the naked eye), and swollen lymph nodes. Skin rashes occur early in the disease, and peeling of the skin in the genital area, hands, and feet may occur in later phases. Some of these symptoms may come and go during the course of the illness.

# Physical Examination
Physical examination of patients with Kawasaki disease is usually remarkable for erythematous rash, irritability, and desquamation of skin and mucous membranes.

# Laboratory Findings
Kawasaki disease is diagnosed by clinical presentation, although the laboratory findings are non-specific for the diagnosis of Kawasaki disease - normocytic anemia, thrombocytosis, with platelets  450103/L  (after first week of acute disease), leucocytosis with white blood cell count  15,000/L, elevated erythrocyte sedimentation rate, elevated liver enzyme levels, hypoalbuminemia with  3.0g/dL, elevated c-reactive protein, hyponatremia and sterile pyuria can be noted on laboratory investigations.

# Electrocardiogram
Electrocardiogram in Kawasaki disease may demonstrate evidence of ventricular dysfunction or, occasionally arrhythmia due to myocarditis. However, in acute disease the electrocardiogram may demonstrate prolonged PR interval, non-specific ST changes, T-wave changes and increased Q/R ratio, which are consistent with myocarditis.

# X Ray
Abnormal findings on chest x-ray may be found in Kawasaki disease, however, they are non-specific and may include; peribronchial cuffing, reticulogranular pattern, pleural effusion, atelectasis and air trapping. In rare circumstances, several years after resolution of the first episode within the elderly population, calcifications of the coronary artery will lead to coronary artery aneurysms. These aneurysms may be visualized using a plain radiograph. This presentation is described as an Aunt Minnie sequelae of Kawasaki disease.

# Echocardiography and ultrasound
An ECG may be helpful in the diagnosis of Kawasaki disease. Findings on an ECG suggestive of Kawasaki disease include coronary artery dilatations, stenosis or aneurysms. Ultrasound may show hydrops (enlargement) of the gallbladder.

# CT scan
CT angiography scan may be helpful in the diagnosis of Kawasaki disease. Findings on CT scan suggestive of Kawasaki disease include small coronary artery dilatations, aneurysms or stenoses. Angiography is the most sensitive and specific for assessment of the vessels.

# MRI
There are no MRI findings associated with Kawasaki disease, however, magnetic resonance angiography can accurately define coronary artery aneurysms in patients with Kawasaki disease.

# Other Imaging Findings
There are no other imaging findings associated with Kawasaki disease.

# Other Diagnostic Studies
Apart from the imaging studies already discussed previously, urinalysis, lumbar puncture, biomarkers and angiography may be helpful in the diagnosis of Kawasaki disease. Findings suggestive of Kawasaki disease include the presence of white blood cells, leukocytosis and coronary artery aneurysms, respectively.

# Treatment

## Medical Therapy
Intravenous immunoglobulin (IVIG) and aspirin are indicated in the treatment of Kawasaki Disease.  It is imperative that treatment be started as soon as the diagnosis is made to prevent damage to the coronary arteries.  Kawasaki disease and a couple of other indications are an exception to the use of aspirin in children, aspirin is otherwise normally not recommended for children due to its association with Reye's syndrome.  Children with Kawasaki disease should be hospitalized.

## Surgery
Mechanical revascularization  may be attempted in patients with coronary artery compromise.

# Prevention
Primary prevention for Kawasaki disease is not applicable. Complications of the disease, however, may be prevented through the use of medical prophylaxis.