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Disease Profile

Familial hemophagocytic lymphohistiocytosis

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Familial erythrophagocytic lymphohistiocytosis; Familial histiocytic reticulosis; FHL;


Congenital and Genetic Diseases; Immune System Diseases; Nervous System Diseases


Hemophagocytic lymphohistiocytosis (HLH) is a condition in which the body makes too many activated immune cells (macrophages and lymphocytes).[1] People with HLH usually develop symptoms within the first months or years of life. Symptoms may include fever, enlarged liver or spleen, cytopenia (decreased number of blood cells), and neurological abnormalities.[2][3] HLH may be inherited in an autosomal recessive manner or it can have non-genetic causes in which case it is called acquired HLH. There are five subtypes of inherited HLH which are designated as familial HLH, types 1-5. Each subtype is caused by a change (mutation) in a different gene. The genetic cause of type 1 is currently unknown. Types 2-5 are caused by mutations in the PRF1 gene, the UNC13D gene, the STX11 gene and the STXBP2 gene, respectively.[4] Treatment depends on a number of factors, including the severity of symptoms, the age of onset, and the underlying cause of the condition.[4][5]

When HLH results from an inappropriate immune response to Epstein-Barr virus or another viral illness, it may be due to a separate genetic condition called X-linked lymphoproliferative disease (XLP). XLP is caused by a mutation in the SH2D1A or XIAP gene and is inherited in an X-linked manner.[6]


The signs and symptoms of hemophagocytic lymphohistiocytosis typically develop during the first months or years of life. However, in rare cases, affected people may not show symptoms until later in childhood or even into adulthood. The features of this condition may include:[1][2][3][4]

  • Fever
  • Enlarged liver and/or spleen
  • Skin rash
  • Lymph node enlargement
  • Breathing problems
  • Easy bruising and/or abnormal bleeding
  • Kidney abnormalities
  • Heart problems
  • Increased risk for certain cancers (leukemia, lymphoma)

Many people with this condition also develop neurologic abnormalities. The neurological symptoms vary but may include irritability, fatigue, abnormal muscle tone, seizures, neck stiffness, mental status changes, ataxia, blindness, paralysis, and/or coma.[1][4]


There are inherited and non-inherited (acquired) causes of hemophagocytic lymphohistiocytosis (HLH).[3][7]

There are five subtypes of inherited (or familial) HLH which are designated familial HLH, types 1-5. Each subtype is caused by a change (mutation) in a different gene that helps regulate the immune system. Type 1 is due to a gene defect on chromosome 9. Familial HLH, type 2 is caused by mutations in the PRF1 gene. Familial HLH, type 3 is caused by mutations in the UNC13D gene. Familial HLH, type 4 is caused by mutations in the STX11 gene. Familial HLH, type 5 is caused by mutations in the STXBP2 gene.[4] 

All of the genes involved with HLH normally provide instructions for proteins that help destroy or turn off activated immune cells when they are no longer needed. Changes in these genes lead to an overproduction of immune cells which results in an excessive immune response and the many signs and symptoms of familial HLH.[1][3][7]

The acquired causes of HLH include: infection, medications that suppress the immune system, autoimmune diseases, immunodeficiencies, certain types of cancer and/or metabolic diseases.[3][7]

When HLH results from an inappropriate immune response to Epstein-Barr virus or another viral illness, it may be due to a separate genetic condition called X-linked lymphoproliferative disease (XLP). XLP is caused by a mutation in the SH2D1A or XIAP gene and is inherited in an X-linked manner.[6]


The diagnosis of hemophagocytic lymphohistiocytosis (HLH) can be established if 1 and/or 2 below is fullfilled:[4][8]

1. A genetic test identifying a mutation in one of the genes involved with this condition

2. At least five out of the following 8 signs or symptoms:

  • Fever
  • Enlarged spleen
  • Cytopenia (lower-than-normal number of blood cells)
  • Elevated levels of triglycerides or low levels of fibrinogen in the blood
  • Hemophagocytosis (the destruction of certain types of blood cells by histiocytes) on bone marrow, spleen or lymph node biopsy
  • Decreased or absent NK cell activity
  • High levels of ferritin in the blood
  • Elevated blood levels of CD25 (a measure of prolonged immune cell activation).

Clinical genetic testing is available for the four genes known to cause familial hemophagocytic lymphohistiocytosis, types 2-5. The Genetic Testing Registry (GTR) is a centralized online resource for information about genetic tests. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


The best treatment options for hemophagocytic lymphohistiocytosis (HLH) are determined by a number of factors, including the severity of symptoms, the age of onset, and the underlying cause of the condition.

In acquired HLH, it is often necessary to treat the underlying condition. For example, antiobiotics or antiviral medications can be used to treat or prevent infections that may have triggered the exaggerated immune response.

Allogeneic hematopoietic cell transplantation is considered a cure for familial HLH. It is often recommended that people with confirmed or suspected familial HLH undergo this treatment as early in life as possible. Prior to hematopoietic cell transplanation, people with HLH are usually treated with chemotherapy and/or immunotherapy to destroy excess immune cells which can lead to life-threatening inflammation.[4][5][3][7]

Please visit the Histiocyte Society to learn more about the treatment guidelines for HLH.

FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

  • Emapalumab(Brand name: Gamifant) Manufactured by NovImmune S.A.
    FDA-approved indication: November 2018, emapalumab (Gamifant) was approved for the treatment of adult and pediatric (newborn and older) patients with primary hemophagocytic lymphohistiocytosis (HLH) with refractory, recurrent, or progressive disease or intolerance of conventional HLH therapy.


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Providing General Support

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

      In-Depth Information

      • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for Familial hemophagocytic lymphohistiocytosis in a table called Phenotypic Series. Each entry in OMIM includes a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
      • PubMed is a searchable database of medical literature and lists journal articles that discuss Familial hemophagocytic lymphohistiocytosis. Click on the link to view a sample search on this topic.

        Selected Full-Text Journal Articles


          1. Familial hemophagocytic lymphohistiocytosis. Genetics Home Reference. November 2014; https://ghr.nlm.nih.gov/condition/familial-hemophagocytic-lymphohistiocytosis.
          2. Kenneth L McClain, MD, PhD. Clinical features and diagnosis of hemophagocytic lymphohistiocytosis. UpToDate. July 29, 2015;
          3. George MR.. Hemophagocytic lymphohistiocytosis: review of etiologies and management.. J Blood Med. June 2014; 5:69-86. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4062561/.
          4. Kejian Zhang, MD, MBA, Alexandra H Filipovich, MD, Judith Johnson, MS, Rebecca A Marsh, MD, and Joyce Villanueva, MT, MBA.. Hemophagocytic Lymphohistiocytosis, Familial. GeneReviews. January 17, 2013; https://www.ncbi.nlm.nih.gov/books/NBK1444/.
          5. Kenneth L McClain, MD, PhD. Treatment and prognosis of hemophagocytic lymphohistiocytosis. UpToDate. October 15, 2015;
          6. Zhang K, Wakefield E, and Marsh R. Lymphoproliferative Disease, X-Linked. GeneReviews. June 30, 2016; https://www.ncbi.nlm.nih.gov/books/NBK1406/.
          7. Janka GE, Lehmberg K.. Hemophagocytic lymphohistiocytosis: pathogenesis and treatment.. Hematology Am Soc Hematol Educ Program. 2013; 2013:605-611. https://www.ncbi.nlm.nih.gov/pubmed/24319239.
          8. Zhang L, Zhou J & Sokol L. Hereditary and acquired hemophagocytic lymphohistiocytosis. Cancer Control. October 2014; 21(4):301-312.
          9. Schwartz RA. Lymphohistiocytosis (Hemophagocytic Lymphohistiocytosis). Medscape. 2016; https://emedicine.medscape.com/article/986458-overview.

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