What is Histiocytosis
What is Histiocytosis?
Histiocytic Disorders and Rare Diseases – together we will find a cure!

Histiocytosis is an umbrella term applied to a group of rare diseases, characterised by increased numbers of white blood cells called histiocytes in the blood and tissues. In all forms of histiocytosis, these cells, which are part of the protective immune system, begin to attack the body, targeting many organs of the body including the bone marrow, liver, spleen, lungs, skin, bone and brain. The prognosis for patients varies greatly depending on the form of histiocytosis.

There are two main groups.
The first group is called a dendritic cell disorder, and the most common disease in this group is Langerhans Cell Histiocytosis (LCH) previously known as Histiocytosis X. Also included in this group are more rare diseases, juvenile xanthogranuloma (JXG) and Erdheim-Chester Disease (ECD).

Langerhans Cell Histiocytosis, LCH for short, histiocytes called Langerhans cells, which are normally found in the skin, may spread to many organs and damage them, so that the symptoms vary depending on which organs are affected, but skin rashes, destruction of bone, breathing problems and damage to the brain are common.

LCH occurs in children, often during infancy but also in adults. It is usually a chronic disease and may cause severe disabilities due to brain damage. The diagnosis is made by microscopic examination of a tissue specimen obtained by biopsy. The prognosis depends very much on the extent of disease and organs affected, which can be assessed by imaging studies. LCH is thought to be caused by alterations in the DNA of Langerhans cells.

The second group is called a macrophage cell disorder, and includes primarily Haemophagocytic Lymphohistiocytosis (HLH) and Rosai-Dorfman Disease (RD).

How to explain Histiocytosis

How to explain Histiocytosis

Haemophagocytic Lymphohistiocytosis HLH for short. In this disease a virus infection triggers another type of histiocyte, the macrophage, to become over active and attack the body. Red blood cells and other white blood cells are engulfed and destroyed by the macrophages, so that the patient is unable to fight infections.


Patients therefore suffer from high fevers, may become anaemic and often have skin rashes, as well as symptoms due to the infecting virus. HLH is an acute and life threatening disease. It frequently occurs in childhood but may occur at any age.

Diagnosis depends on detection of the infecting organism and demonstration of macrophages engulfing other cells as well as other abnormalities of white blood cells, usually in sample of bone marrow. In familial forms of HLH, abnormal genes, which alter white blood cell function, are passed from the parents to children.

Rarer Forms - there are other even rarer forms of histocytosis related to both LCH and HLH and very rarely malignant histiocytosis occurs, which is a leukaemia-like disease of histiocytes.

Please be advised that all the information you read here is not a replacement for the advice you will get from your consultant and their team.

Help ensure that we can continue to bring you this vital informational material, make a donation today

Frequently Asked Questions

Histiocytic Disorders and Rare Diseases

Why are all of these diseases with different names considered to be related to each other?
All of the diseases are caused by the over-production of white blood cells called histiocytes. Their different classifications depend on the type of histiocyte involved.

Where can I find reliable information about histiocytosis?
Histiocytosis UK online community provides a number of informational documents and articles, as well as links to medical articles about the histiocytic disorders. While the Internet does provide a significant volume of information about histiocytic disorders, some of this information is not accurate. It is important to look for documents that are current, are free of grammatical and spelling errors, appear to be objective, are free of advertisements, and clearly state their sources.

How to explain Histiocytosis

How to explain Histiocytosis

How can I explain histiocytosis to family and friends?
Histiocytosis is a rare disease that is caused by the over-production of a type of white cell that can lead to organ damage and the formation of tumors. The Histiocytosis UK FAQ pages are also a great way to help explain these complicated diseases to family and friends.


What is Rare Disease?

  • A rare disease is defined by the European Union as one that affects less than 5 in 10,000 of the general population.
  • There are between 6,000 and 8,000 known rare diseases.
  • Around five new rare diseases are described in medical literature each week.
  • 1 in 17 people, or 7% of the population, will be affected by a rare disease at some point in their lives.
  • This equates to approximately 3.5 million people in the UK and 30 million people across Europe.
  • In the UK, a single rare disease may affect up to about 30,000 people.
  • The vast majority of rare diseases will affect far fewer than this – some will affect only a handful, or even a single person in the whole of the UK.
  • 80% of rare diseases have a genetic component.
  • Often rare diseases are chronic and life-threatening.
  • Rare diseases can be single gene, multifactorial, chromosomal or non-genetic.
  • 75% of rare diseases affect children, and 30% of rare disease patients die before their fifth birthday.

Where can I learn more about rare diseases in general?
Rare Disease UK (RDUK) is the national alliance for people with rare diseases and all who support them. www.raredisease.org.uk.
Orphanet – Database/information about rare diseases with translation available in numerous languages. http://www.ojrd.com
Please be advised that all the information you read here is not a replacement for the advice you will get from your consultant and their team.

Help ensure that we can continue to bring you this vital informational material, make a donation today

LCH Newsfeed

pubmed: histiocytosis

NCBI: db=pubmed; Term=histiocytosis

Icon for Elsevier Science Related Articles

Erdheim-Chester Disease.

Mayo Clin Proc. 2019 05;94(5):924-925

Authors: Poellinger A, Hrycyk J

PMID: 31054617 [PubMed - indexed for MEDLINE]

Icon for Elsevier Science Related Articles

Hemophagocytic Lymphohistiocytosis in the Elderly.

Am J Med Sci. 2019 01;357(1):67-74

Authors: Altook R, Ruzieh M, Singh A, Alamoudi W, Moussa Z, Alim H, Safi F, Duggan J

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease of massive, dysregulated cytokine release and secondary multiorgan failure and is associated with high mortality. Primary HLH occurs predominately in infants and young children with a genetic predisposition. Acquired HLH is less well characterized and usually occurs in younger adults in the setting of severe inflammation triggered by infection or malignancy. Little is known about the disease in elderly. We report 3 patients >50 years old who presented with multiorgan failure and shock without an identifiable source and were ultimately diagnosed with acquired HLH. We performed a literature review of HLH in adults >50 years of age and identified an additional 68 cases. Mean age was 62 years, with male predominance. Most cases were triggered by infection (49%) followed by malignancy (27%). Nineteen patients were treated with the HLH-94 protocol, 11 received corticosteroids and the remainder received non-HLH specific interventions. Overall mortality was 62%.

PMID: 30278875 [PubMed - indexed for MEDLINE]

Icon for Wolters Kluwer Related Articles

Hepatobiliary Dysfunction and Disseminated Intravascular Coagulation Increase Risk of Mortality in Pediatric Hemophagocytic Lymphohistiocytosis.

Pediatr Crit Care Med. 2018 10;19(10):e522-e530

Authors: Goldman J, Desai MS, McClain KL, Tcharmtchi MH, Kennedy CE, Thompson K, Lam F, Bashir DA, Chinn IK, Goldberg BR, Allen CE, Nguyen TC

OBJECTIVES: Hemophagocytic lymphohistiocytosis poses significant challenges due to limited tools to guide clinical decisions in a population at high risk of death. We sought to assess whether disseminated intravascular coagulation and hepatobiliary dysfunction, significant comorbidities seen in critical care settings, would identify hemophagocytic lymphohistiocytosis patients with increased risk of mortality.
DESIGN: Retrospective chart review.
SETTING: Single-center PICU.
PATIENTS: All patients admitted to a tertiary care children's hospital diagnosed with hemophagocytic lymphohistiocytosis from 2005 to 2012.
MEASUREMENTS AND MAIN RESULTS: Forty-three patients were diagnosed with hemophagocytic lymphohistiocytosis with median age of 61 months. The 5-year overall survival was 51% (22/43). Univariate analyses revealed ferritin levels greater than 10,000 (ng/mL), international normalized ratio greater than 1.5, or platelet counts less than 100,000/µL at initiation of dexamethasone were individually associated with mortality. Development of disseminated intravascular coagulation, hepatobiliary dysfunction, or both increased the likelihood of death in hemophagocytic lymphohistiocytosis patients (relative risk; 95% CI) (6; 1.4-34; p < 0.05), (4.1; 1.8-10; p < 0.05), and (7.5; 1.8-42; p < 0.05). Of 12 autopsies performed, 75% had at least one active infection, 66% had chronic lymphopenia, 50% had lymphocyte depletion in the spleen, thymus, or bone marrow, 42% had evidence of microvascular thrombosis, and 92% had evidence of hepatocellular injury.
CONCLUSIONS: Hemophagocytic lymphohistiocytosis continues to have high mortality with hemophagocytic lymphohistiocytosis-1994/2004 (dexamethasone/etoposide), the current standard of care for all children with hemophagocytic lymphohistiocytosis. Hemophagocytic lymphohistiocytosis patients who developed disseminated intravascular coagulation, hepatobiliary dysfunction, or both had higher risk of death with mortalities of 60%, 77%, and 77%, respectively. Phenotypic classifications are urgently needed to guide individualized treatment strategies to improve outcomes for children with hemophagocytic lymphohistiocytosis.

PMID: 30113519 [PubMed - indexed for MEDLINE]

Please use the form below to contact Histio UK

When we are out of the office and over holiday periods we have limited access to email and telephone. We will respond to your enquiry as soon as it is possible or upon our return. Thank You.

Telephone: 01733 309619 - Please note this is not a 24 hour number - 9am to 5.30pm

Your Name (required)

Your Email (required)


Your Message

Please answer the question