Hemophagocytic lymphohistiocytosis (HLH) is an aggressive and life-threatening condition of the immune system. Your immune system defends against infections and keeps you healthy. In HLH, the immune system gets confused. Sometimes, it works too much, causing excessive inflammation and tissue damage. Other times, the immune system fails to work normally, leaving patients at risk for serious infections.
The abnormal cells in HLH are called histiocytes. Normal histiocytes are a type of white blood cell found in the blood and in organs such as the lymph nodes, spleen and liver. Normal histiocytes help control infections and remove dead cells from the body.
With HLH, histiocytes become overactive and begin to attack the body’s own tissues as if they are invading organisms. The result can be damage to organs such as the brain, liver and bone marrow. HLH causes histiocytes to release chemicals into the blood and ingest other cells, mistaking them for an infection. These confused histiocytes tend to accumulate in areas where they should not. This buildup and cell destruction can lead to organ damage and multi-organ failure.
HLH is primarily a condition that affects infants and small children. About 70 percent of cases occur before the age of 1. If untreated, HLH can become fatal very quickly. It is important to recognize and begin treatment as soon as possible since the condition can progress very rapidly.
There are two types of HLH: primary and secondary. They can be difficult to tell apart because symptoms can be similar. Doctors at Riley at IU Health do special genetic testing to make the correct diagnosis. The two types of HLH are:
Initially, HLH appears to be a routine febrile (fever) illness, but it lasts longer and children begin showing symptoms uncommon in typical infections, such as yellowing, pale or bruised skin. Symptoms depend on where the histiocytes (abnormal cells) accumulate.
Symptoms of hemophagocytic lymphohistiocytosis include:
In addition to taking your child’s medical history and obtaining a thorough family history, your child’s doctor will examine him or her carefully. A doctor who suspects HLH will probably request many tests, which may include:
Because HLH can become fatal quickly, your child’s doctor may decide to start treatment even before the genetic test results are known. Even though HLH is not cancer, chemotherapy is often needed. The goal is to calm the overactive immune system. Limiting immune system function slows the damage HLH does to the body. At the same time, it is important to prevent and treat infections with antibiotics and other medicines. Children being treated for HLH can be very sick and need help breathing. Many children will require blood transfusions.
The only cure for primary HLH is a stem cell transplant in which bone marrow from a healthy donor is transplanted into your child’s bones. For children with secondary HLH, chemotherapy and immunosuppression may be enough.
HLH is a serious condition. HLH and the procedures used to treat it can be fatal. However, follow-up with survivors indicates that most of them return to a normal or near-normal life.
For proper, successful treatment and good long-term prospects, children with HLH should be diagnosed and treated at a pediatric stem cell transplant center with experience dealing with HLH.
Visit the source listed below to learn more about HLH.
Riley at IU Health offers a broad range of supportive services to make life better for families who choose us for their children's care.
The Histiocytosis Association helps patients and families learn to manage HLH and supports research for a cure. The organization's website shares information about the condition, current research initiatives and more.
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