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Also called: Familial Erythrophagocytic Lymphohistiocytosis
Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder in which the immune system does not work properly.
In healthy people, white blood cells are part of the immune system that help fight infection. Two important kinds of white blood cells are called cytotoxic T cells and natural killer cells. These white blood cells kill cells that have been infected with viruses or other germs. These cells also make chemicals called cytokines. Cytokines are released into the blood. They attract cells to the infection site and help regulate the immune response.
In patients with HLH, cytotoxic T cells and natural killer cells do not kill infected cells as well as they should. That makes it harder for people with HLH to fight infections. They often develop repeated episodes of hyperinflammation. Hyperinflammation is when the immune system is overly activated from cytotoxic T cells and natural killer cells making too many cytokines. These cells damage parts of the body, such as the liver, spleen, bone marrow, and brain.
Without treatment, HLH can lead to severe organ damage and death.
Some of the more common symptoms of HLH include:
There are 2 main types of HLH:
Genes carry information telling cells within the body how to grow and function. Most cases of familial HLH are caused by a gene change (mutation) in the genes PRF1, UNC13D, STX11, or STXBP2. These genes help white blood cells kill invading viruses and other germs. They also work to calm the immune system once it becomes activated.
Most people have 2 working copies of each of these genes. One copy is inherited from the mother and another from the father. Familial HLH occurs when someone inherits an HLH gene mutation from the mother and another mutation in the same HLH gene from the father. Parents of a child with familial HLH have a 25% or 1 in 4 chance with each pregnancy of having another child with familial HLH.
HLH is diagnosed in fewer than 1 out of every 50,000–100,000 children each year. The condition occurs equally often in boys and girls. The symptoms of HLH look like many other disorders. As a result, doctors think that more children develop HLH than are recognized and reported.
Tests for HLH may include:
Treatment of HLH depends on the underlying cause and severity of symptoms. HLH is a complex condition. Parents should look for a health care provider who knows this condition well. Only a health care provider who is familiar with the condition should offer treatment for HLH.
For children with familial HLH, the first step is to suppress the overactive immune system by reducing the number of activated immune cells and the cytokines. This is often done using a combination of steroids, cytokine inhibitors, and chemotherapy. Cytokine inhibitors such as emapalumab or ruxolitinib reduce the cytokine activity involved in the development of HLH. The goal is to put the condition in remission.
After this treatment, children with familial HLH usually undergo an allogeneic stem cell transplant. This procedure replaces the unhealthy immune system with a healthy one from a different person. This offers the best chance of a cure.
For children with acquired HLH, the goal is to identify and treat the underlying cause (such as an infection, cancer, or autoimmune condition). In many cases, this treatment puts the acquired HLH into remission. But sometimes health care providers will suggest steroids, medicines to inhibit cytokines, chemotherapy, or a combination of therapies.
Health care providers decide to use steroids, cytokine inhibitors, or chemotherapy based on how severe the HLH is. They do not make these decisions based on whether it is familial or acquired.
People of any age with familial HLH should try to limit their exposure to infections of any kind. It is important to seek medical help if anything unusual appears. When a child has familial HLH, parents should talk to a genetic counselor about the chances of future children having the same condition.
Genetic counseling and testing can help patients and families understand familial HLH and the risk of passing it on to children.
St. Jude provides the highest quality of care for patients with hemophagocytic lymphohistiocytosis.
Study goal:
The main goal of the study is to create an international database of HLH patient information. This information will help researchers develop clinical trials in the future on new HLH treatments.
Patients accepted to St. Jude must have a disease we treat and must be referred by a physician or other qualified medical professional. We accept most patients based on their ability to enroll in an open clinical trial.
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