medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pract ...

, histiocytosis is an excessive number of

histiocyte A histiocyte is a vertebrate cell that is part of the mononuclear phagocyte system (also known as the reticuloendothelial system or lymphoreticular system). The mononuclear phagocytic system is part of the organism's immune system. The histiocyt ...

s (tissue

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

s), and the term is also often used to refer to a group of rare diseases which share this

sign A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or me ...

as a characteristic. Occasionally and confusingly, the term "histiocytosis" is sometimes used to refer to individual diseases. According to the

Histiocytosis Association of America In medicine, histiocytosis is an excessive number of histiocytes (tissue macrophages), and the term is also often used to refer to a group of rare diseases which share this sign as a characteristic. Occasionally and confusingly, the term "histi ...

, 1 in 200,000 children in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

are born with histiocytosis each year. HAA also states that most of the people diagnosed with histiocytosis are children under the age of 10, although the disease can afflict adults. The disease usually occurs from birth to age 15. Histiocytosis (and

malignant histiocytosis Malignant histiocytosis is a rare hereditary disease found in the Bernese Mountain Dog and humans, characterized by histiocytic infiltration of the lungs and lymph nodes. The liver, spleen, and central nervous system can also be affected. Histio ...

) are both important in veterinary as well as human pathology.

Diagnosis

Sinus histiocytosis (intermediate magnification)

Histiocytosis is a rare disease, thus its diagnosis may be challenging. A variety of tests may be used, including: * Imaging ** CT scans of various organs such as lung, heart and kidneys. **

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

of the brain, pituitary gland, heart, among other organs. ** Skeletal survey is useful in children **

Ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...

of liver and spleen * Blood tests: measure cell counts and inflammation * Breathing tests * Tissue biopsy and molecular testing to detect mutations

Classification

There are competing systems for classifying histiocytoses. According to the 1999 classification proposed by the

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...

, they can be divided into three categories. However, the classifications in ICD10 and MeSH are slightly different, as shown below: Alternatively, histiocytoses may be divided into the following groups: *

X-type histiocytoses X-type histiocytoses are a clinically well-defined group of cutaneous syndromes characterized by infiltrates of Langerhans cells, as opposed to Non-X histiocytosis in which the infiltrates contain monocytes/macrophages. Conditions included in thi ...

Non-X histiocytoses Non-X histiocytoses are a clinically well-defined group of cutaneous syndromes characterized by infiltrates of monocytes/macrophages, as opposed to X-type histiocytoses in which the infiltrates contain Langerhans cells. Conditions included in th ...

Lymphohistiocytosis is a similar immune system disease characterized by the inappropriate activation of natural killer cells, CD8+ cytotoxic T-cells, and macrophages, involving principally the liver, spleen and central nervous system and associated with severe lymphoid atrophy.

Treatments

Various treatments exist for histiocytosis. The one selected depends on the location of the disease and the patient history. The modalities use may include: *

Chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...

Cladribine Cladribine, sold under the brand name Leustatin, among others, is a medication used to treat hairy cell leukemia (leukemic reticuloendotheliosis) and B-cell chronic lymphocytic leukemia. Cladribine, sold under the brand name Mavenclad, is indicat ...

(also known as 2CDA or Leustatin) **

Etoposide Etoposide, sold under the brand name Vepesid among others, is a chemotherapy medication used for the treatments of a number of types of cancer including testicular cancer, lung cancer, lymphoma, leukemia, neuroblastoma, and ovarian cancer. It is ...

Methotrexate Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...

6-mercaptopurine Mercaptopurine (6-MP), sold under the brand name Purinethol among others, is a medication used for cancer and autoimmune diseases. Specifically it is used to treat acute lymphocytic leukemia (ALL), acute promyelocytic leukemia (APL), Crohn's d ...

Vinblastine Vinblastine (VBL), sold under the brand name Velban among others, is a chemotherapy medication, typically used with other medications, to treat a number of types of cancer. This includes Hodgkin's lymphoma, non-small cell lung cancer, bladder ca ...

* Surgery *

Radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

Society

Patients and families can gain support and educational materials from the Histiocytosis Association The Histiocyte Society, a nonprofit organization, is a group of more than 200 physicians and scientists from around the world committed to improving the lives of patients with histiocytic disorders by conducting clinical and laboratory research into the causes and treatment of this disease. The Society has instituted several clinical trials and treatment plans. The NACHO is a group of institutions that collaborate on scientific and clinical research for histiocytic diseases. Established in 2014 by 12 institutions, it was funded through a consortium grant from the St. Baldrick's Foundation.

References

External links

{{Histiocytosis Monocyte- and macrophage-related cutaneous conditions