Reye's syndrome is a very rare but life-threatening disorder that causes inflammation and swelling of the brain and degeneration of the liver.

The cause of Reye's syndrome is unknown, although it typically occurs after infection by certain viruses, such as influenza or varicella (chickenpox), particularly in children who take aspirin. Because of this increased risk of Reye's syndrome, aspirin is not recommended for children, except for the treatment of a few specific diseases. Now that aspirin use has declined—in large part because of the possibility of triggering Reye's syndrome—fewer than 20 children a year develop this disorder. The condition occurs mainly in children younger than 18. In the United States, most cases occur in late fall and winter.

Reye's syndrome begins with the symptoms of a viral infection, such as an upper respiratory tract infection, influenza, or chickenpox. After 5 to 7 days, the child suddenly develops very severe nausea and vomiting. Within a day, the child becomes confused, disoriented, and agitated. These changes in the child's mental condition are sometimes followed by seizures, coma, and death. Degeneration of the liver may lead to blood clotting problems and bleeding. The severity of illness varies greatly. Doctors do blood tests and often do a liver biopsy (the removal of tissue samples for examination) to confirm the diagnosis and to rule out other diseases.

The child's prognosis depends on the amount of swelling in the brain. The overall chances that the child will die are about 20%, but range from less than 2% among children with mild disease to more than 80% among those in a deep coma.

Children who survive the acute phase of the illness usually recover fully. Those with more severe symptoms may later show some evidence of brain damage, such as mental retardation/intellectual disability or a seizure disorder. Abnormal muscle movement or damage to specific nerves may also occur. Reye's syndrome rarely affects a child twice.

There is no specific treatment for Reye's syndrome. Children are placed in intensive care. Vitamin K or fresh frozen plasma is given to help prevent bleeding. Children in a deep coma may require placement of a tube into the windpipe to assist their breathing (endotracheal intubation). To alleviate the swelling and pressure on the brain, doctors restrict fluids, elevate the head of the bed, and give drugs that force the body to get rid of excess water (such as mannitol).

The enteroviruses include numerous strains of coxsackievirus, echovirus, enterovirus, and poliovirus. These viruses are responsible for illness in 10 to 30 million people each year in the United States, primarily in the summer and fall. Infections are highly contagious and typically affect many people in a community, sometimes reaching epidemic proportions. Enteroviral infections are most common among children, particularly those living in conditions of poor hygiene.

The infection begins when material contaminated with the virus is swallowed. The virus then reproduces in the digestive tract. The body's immune defenses stop many infections at this stage, and the result is few or no symptoms. Colds and upper respiratory infections are common outcomes of infection with enteroviruses. Sometimes, the virus survives and spreads into the bloodstream, resulting in fever, headache, sore throat, and, at times, vomiting. People often refer to such illnesses as the "summer flu," although they are not influenza. Some strains of enterovirus also cause a generalized, nonitchy rash on the skin or sores inside the mouth. This type of illness is by far the most common enteroviral infection. Rarely, an enterovirus progresses from this stage to attack a particular organ. The virus can attack many different organs, and the symptoms and severity of disease depend on the specific organ infected. Several diseases are caused by enteroviruses:

• Hand-foot-and-mouth disease affects the skin and mucous membranes, causing painful sores to appear inside the mouth, on the hands and feet, and occasionally on the buttocks or genitals.
• Herpangina also affects the skin and mucous membranes, causing painful sores on the tongue and the back of the throat.
• Aseptic meningitis affects the membranes covering the brain and spinal cord (meninges), causing severe headache, stiff neck, and sensitivity to light.
• Encephalitis affects the brain, causing confusion, weakness, seizures, and coma.
• Paralytic poliomyelitis affects the nervous system, causing weakness of various muscles.
• Myocarditis affects the heart, causing weakness and shortness of breath with exertion.
• Epidemic pleurodynia (Bornholm disease) affects the muscles, causing severe intermittent pain in the wall of the lower chest (adults) or upper abdomen (children).
• Hemorrhagic conjunctivitis affects the eyes, causing painful, red, runny eyes; bleeding under the conjunctiva; and swollen eyelids.

Enteroviral infections usually resolve completely, but infections of the heart or central nervous system are occasionally fatal. There is no cure. Treatment is directed at relieving symptoms.

Kawasaki disease causes inflammation in the walls of blood vessels throughout the body. The cause is unknown, but evidence suggests a virus or other infectious organism triggers an abnormal immune system response in genetically predisposed children. Inflammation of blood vessels in the heart causes the most serious problems.

Most children with Kawasaki disease range in age from 1 to 8 years, although infants and adolescents can be affected. Roughly twice as many boys as girls are affected. The illness is more common among children of Japanese descent. Several thousand cases of Kawasaki disease are estimated to occur in the United States every year.

The illness begins with fever—usually above 102° F (38.9° C)—which rises and falls over 1 to 3 weeks. Within a day or two, the eyes become red but without any discharge. Within 5 days, a red, patchy rash usually appears over the trunk, around the diaper area, and on mucous membranes, such as the lining of the mouth or vagina. The child has a red throat; reddened, dry, cracked lips; and a strawberry-red tongue. Also, the palms and soles turn red or purplish red, and the hands and feet often swell. The skin on the fingers and toes begins to peel about 10 days after the illness starts. The lymph nodes in the neck are often swollen and slightly tender. The illness may last from 2 to 12 weeks or longer.

About 50% of children develop problems involving the heart, such as a rapid or irregular heart beat, usually beginning 1 to 4 weeks after the onset of illness. Half of the children with heart problems develop the most serious heart problem, coronary artery aneurysm (a bulge in the wall of a coronary artery). These aneurysms can rupture or provoke a blood clot, leading to a heart attack and sudden death. Other problems include inflammation of the tissues lining the brain (meningitis), joints, and gallbladder. These symptoms eventually resolve without causing permanent damage. Doctors perform an ultrasound of the heart to detect coronary artery aneurysms.

Children recover completely if their coronary arteries are not affected within the first 8 weeks of illness. For those with coronary artery problems, survival varies with the severity of disease. With treatment, fewer than 0.01% of children with Kawasaki disease in the United States die. Without treatment, the death rate may reach 1%. Of those who die, death typically occurs in the first few months but can occur decades afterward. About 50% of the aneurysms resolve within 1 year. Large aneurysms are less likely to resolve. However, even the ones that resolve may lead to an increased risk of heart problems in adulthood.

Treatment given within 10 days of symptoms significantly reduces the risk of coronary artery damage and speeds the resolution of fever, rash, and discomfort. For 1 to 4 days, high doses of immune globulin are given by vein, and high doses of aspirinSome Trade Names
BAYER
are given by mouth. Once the fever is gone, a lower dose of aspirinSome Trade Names
BAYER
is usually continued for at least 8 weeks. If there are no coronary artery aneurysms and signs of inflammation are gone, aspirinSome Trade Names
BAYER
may be stopped. However, children with coronary artery abnormalities require continuous and long-term treatment with aspirinSome Trade Names
BAYER
. An annual influenza vaccination is indicated for children (6 months of age or older) receiving long-term treatment with aspirinSome Trade Names
BAYER
. If the child contracts influenza or chickenpox, dipyridamoleSome Trade Names
PERSANTINE
is sometimes used temporarily instead of aspirinSome Trade Names
BAYER
to lessen the risk of Reye's syndrome (see see Viral Infections in Infants and Children: What Is Reye's Syndrome?).

Children with large coronary aneurysms may be treated with anticoagulant drugs such as warfarinSome Trade Names
COUMADIN
or dipyridamoleSome Trade Names
PERSANTINE
. Some children may even require coronary artery bypass grafting or, rarely, a heart transplant.