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Familial hemophagocytic lymphohistiocytosis
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Reviewed January 2011
What is familial hemophagocytic lymphohistiocytosis?
Familial hemophagocytic lymphohistiocytosis is a disorder in which the immune system produces too many activated immune cells (lymphocytes) called T cells, natural killer cells, B cells, and macrophages (histiocytes). Excessive amounts of immune system proteins called cytokines are also produced. This overactivation of the immune system causes fever and damages the liver and spleen, resulting in enlargement of these organs.
Familial hemophagocytic lymphohistiocytosis also destroys blood-producing cells in the bone marrow, a process called hemophagocytosis. As a result, affected individuals have low numbers of red blood cells (anemia) and a reduction in the number of blood cells involved in clotting (platelets). A reduction in platelets may cause easy bruising and abnormal bleeding.
The brain may also be affected in familial hemophagocytic lymphohistiocytosis. As a result, affected individuals may experience irritability, delayed closure of the bones of the skull in infants, neck stiffness, abnormal muscle tone, impaired muscle coordination, paralysis, blindness, seizures, and coma. In addition to neurological problems, familial hemophagocytic lymphohistiocytosis can cause abnormalities of the heart, kidneys, and other organs and tissues. Affected individuals also have an increased risk of developing cancers of blood-forming cells (leukemia and lymphoma).
Signs and symptoms of familial hemophagocytic lymphohistiocytosis usually become apparent during infancy, although occasionally they appear later in life. They usually occur when the immune system launches an exaggerated response to an infection, but may also occur in the absence of infection. Without treatment, most people with familial hemophagocytic lymphohistiocytosis survive only a few months.
How common is familial hemophagocytic lymphohistiocytosis?
Familial hemophagocytic lymphohistiocytosis occurs in approximately 1 in 50,000 individuals worldwide.
What genes are related to familial hemophagocytic lymphohistiocytosis?
Familial hemophagocytic lymphohistiocytosis may be caused by mutations in any of several genes. These genes provide instructions for making proteins that help destroy or deactivate lymphocytes that are no longer needed. By controlling the number of activated lymphocytes, these genes help regulate immune system function.
Approximately 40 to 60 percent of cases of familial hemophagocytic lymphohistiocytosis are caused by mutations in the PRF1 or UNC13D genes. Smaller numbers of cases are caused by mutations in other known genes. In some affected individuals, the genetic cause of the disorder is unknown.
The gene mutations that cause familial hemophagocytic lymphohistiocytosis impair the body's ability to regulate the immune system. These changes result in the exaggerated immune response characteristic of this condition.
See a list of genes associated with familial hemophagocytic lymphohistiocytosis.
How do people inherit familial hemophagocytic lymphohistiocytosis?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of familial hemophagocytic lymphohistiocytosis?
These resources address the diagnosis or management of familial hemophagocytic lymphohistiocytosis and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about familial hemophagocytic lymphohistiocytosis?
You may find the following resources about familial hemophagocytic lymphohistiocytosis helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for familial hemophagocytic lymphohistiocytosis?
What if I still have specific questions about familial hemophagocytic lymphohistiocytosis?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding familial hemophagocytic lymphohistiocytosis?
anemia ; autosomal ; autosomal recessive ; bone marrow ; cell ; clotting ; coma ; familial ; fever ; gene ; immune response ; immune system ; infection ; killer cells ; leukemia ; lymphoma ; muscle tone ; natural killer cells ; neurological ; platelets ; recessive ; syndrome
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (12 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.