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.

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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

HLH Newsfeed

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Related Articles

Medical Management of Pulmonary Hypertension with Unclear and/or Multifactorial Mechanisms (Group 5): Is There a Role for Pulmonary Arterial Hypertension Medications?

Curr Hypertens Rep. 2017 Oct 18;19(11):86

Authors: Weatherald J, Savale L, Humbert M

PURPOSE OF REVIEW: The purpose of this review was to outline the mechanisms and to review recent literature on pulmonary arterial hypertension (PAH) medications in group 5 pulmonary hypertension (PH).
RECENT FINDINGS: The first steps in management are to understand the mechanisms and hemodynamic profile and to exclude chronic thromboembolic disease. Recent studies in the past 5 years have found that PAH medications may improve hemodynamics in patients with pre-capillary pulmonary hypertension due to sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, and myeloproliferative disorders with dasatinib-induced PH. Improvements in exercise capacity are uncommon, and no survival benefit has been demonstrated. There is a risk of pulmonary edema in patients with pulmonary venous involvement or fibrosing mediastinitis when treated with PAH therapies. There is limited evidence supporting the use of PAH medications in group 5 patients, and they may be harmful in certain cases. In most patients with group 5 PH, treatment should be directed to the underlying disease with PAH therapies reserved for patients with severe pre-capillary PH.

PMID: 29046979 [PubMed - in process]

Related Articles

Elevation of CD16(+)CD56(+) NK-cells and down-regulation of serum interleukin-21 (IL-21) and IL-1α after splenectomy in relapsed hemophagocytic lymphohistiocytosis of unknown cause.

Hematology. 2017 Sep;22(8):477-483

Authors: Wang J, Han W, Gao Z, Wang Y, Wu L, Zhang J, Lai W, Wang Z

OBJECTIVES: Encouraging progress has been made in application of splenectomy in the treatment of relapsed hemophagocytic lymphohistiocytosis (HLH) of unknown cause. The aim was to determine the roles of lymphocyte subpopulations and inflammatory cytokines in splenectomy.
METHODS: We retrospectively analyzed changes in lymphocyte subpopulations and levels of inflammatory cytokines at different time-points before and after splenectomy in the patients with relapsed HLH of unknown cause, as well as the correlations between these changes and the disease prognosis.
RESULTS: During the period from June 2006 to June 2016, we enrolled 107 patients with relapsed HLH of unknown cause, of whom 29 were treated with splenectomy. Among the 29 patients, 7 cases were non-Hodgkin lymphomas based on spleen pathology, 1 case withdrew and the remaining 21 non-lymphoma cases were available for analysis. Results showed a significant increase in both percentage of CD16(+)CD56(+) NK cells (P = 0.003) and NK cell activity (P = 0.028) at 24 wk after splenectomy compared to their baseline pre-surgery levels. We also examined seven patients for the changes in cytokine levels before and after splenectomy and found that IL-21 and IL-1α decreased at 4 wk after splenectomy (P < 0.05). Seven non-lymphoma patients determined as no response to treatment (NR) prior to splenectomy had significantly longer survival (P = 0.001) compared to the 24 patients with relapsed HLH of unknown cause who were also determined as NR but not treated by splenectomy.
DISCUSSION: Splenectomy can improve clinical symptoms and survival of patients with relapsed HLH of unknown cause. The mechanism is likely related to the changes in percent NK cells and cytokines (IL-21 and IL-1α) after surgery.

PMID: 28413901 [PubMed - indexed for MEDLINE]

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Adult Niemann-Pick disease type B with myositis ossificans: a case report.

Acta Reumatol Port. 2016 Jul-Sep;41(3):260-264

Authors: Shumnalieva R, Monov S, Shoumnalieva-Ivanova V, Rashkov R

Niemann-Pick Disease (NPD) is a rare autosomal recessive lysosomal lipid storage disorder. The disease is caused by gene mutations that affect the metabolism of sphingolipids. The dysfunctions cause sphingomyelin to accumulate in different organs. NPD includes forms with low and high levels of sphingomyelin. We report a case of a 34 year-old man with a family history of NPD type B who presented with hepatosplenomegaly, neurological deficiency, bone abnormalities, and myositis ossificans. The clinical, biochemical, and imaging data confirmed the combined diagnosis of NPD type B with myositis ossificans.

PMID: 26338042 [PubMed - indexed for MEDLINE]

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Cytomegalovirus-Induced Hemophagocytic Lymphohistiocytosis in an Extreme Preterm Infant: Recognition and Therapy Leading to Recovery.

Adv Neonatal Care. 2017 Apr;17(2):91-95

Authors: Halliday M, Ross J, Southgate WM

BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) is a rare disease that can be triggered by cytomegalovirus, a relatively common infectious exposure to neonates. The clinical presentation is common to many acute illnesses seen in extreme premature infants; however, there are key clinical and laboratory findings that can lead to the diagnosis.
PURPOSE: We present a case of an extreme premature infant of 25 weeks' gestation who developed cytomegalovirus-induced HLH. Using the current published protocols that are used in pediatric cancer can be adapted for use in a premature infant, which led to remission of HLH and eventual discharge from the neonatal intensive care unit.
IMPLICATIONS FOR PRACTICE: There are published treatment protocols used in pediatric oncology that when initiated early can lead to favorable outcomes and remission in even the most fragile neonates.
IMPLICATIONS FOR RESEARCH: Additional studies are needed on the pharmacokinetics, dosing, and side effects on medications used for treatment of HLH in preterm infants. Additional research is needed to improve the clinician's ability to reach the diagnosis as well as define treatment strategies that provide optimal outcomes.

PMID: 27501069 [PubMed - indexed for MEDLINE]

Related Articles

Spectrum of SMPD1 mutations in Asian-Indian patients with acid sphingomyelinase (ASM)-deficient Niemann-Pick disease.

Am J Med Genet A. 2016 Oct;170(10):2719-30

Authors: Ranganath P, Matta D, Bhavani GS, Wangnekar S, Jain JM, Verma IC, Kabra M, Puri RD, Danda S, Gupta N, Girisha KM, Sankar VH, Patil SJ, Ramadevi AR, Bhat M, Gowrishankar K, Mandal K, Aggarwal S, Tamhankar PM, Tilak P, Phadke SR, Dalal A

Acid sphingomyelinase (ASM)-deficient Niemann-Pick disease is an autosomal recessive lysosomal storage disorder caused by biallelic mutations in the SMPD1 gene. To date, around 185 mutations have been reported in patients with ASM-deficient NPD world-wide, but the mutation spectrum of this disease in India has not yet been reported. The aim of this study was to ascertain the mutation profile in Indian patients with ASM-deficient NPD. We sequenced SMPD1 in 60 unrelated families affected with ASM-deficient NPD. A total of 45 distinct pathogenic sequence variants were found, of which 14 were known and 31 were novel. The variants included 30 missense, 4 nonsense, and 9 frameshift (7 single base deletions and 2 single base insertions) mutations, 1 indel, and 1 intronic duplication. The pathogenicity of the novel mutations was inferred with the help of the mutation prediction software MutationTaster, SIFT, Polyphen-2, PROVEAN, and HANSA. The effects of the identified sequence variants on the protein structure were studied using the structure modeled with the help of the SWISS-MODEL workspace program. The p. (Arg542*) (c.1624C>T) mutation was the most commonly identified mutation, found in 22% (26 out of 120) of the alleles tested, but haplotype analysis for this mutation did not identify a founder effect for the Indian population. To the best of our knowledge, this is the largest study on mutation analysis of patients with ASM-deficient Niemann-Pick disease reported in literature and also the first study on the SMPD1 gene mutation spectrum in India. © 2016 Wiley Periodicals, Inc.

PMID: 27338287 [PubMed - indexed for MEDLINE]

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