Histiocytosis

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 "histiocytosis" is sometimes used to refer to individual diseases.

According to the Histiocytosis Association of America, 1 in 200,000 children in the United States 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) are both important in veterinary as well as human pathology.

Types

Types of LCH have also been known as "eosinophilic granuloma", "Hand-Schuller-Christian disease", "Letterer-Siwe disease", and "histiocytosis X". (See the article Langerhans cell histiocytosis for details).

Alternatively, histiocytoses may be divided into the following groups:^:714–724

• X-type histiocytoses
• Non-X histiocytoses

Lymphohistiocytosis is "a widespread infiltrate of non-malignant lymphocytes and macrophages, involving principally the liver, spleen and central nervous system and associated with a severe lymphoid atrophy."

Diagnosis

Sinus histiocytosis, a common feature in lymph node biopsies, is characterized by dilated sinuses containing variable numbers of histiocytes.

Classification

There are competing systems for classifying histiocytoses. According to the 1999 classification proposed by the World Health Organization, they can be divided into three categories. However, the classifications in ICD10 and MeSH are slightly different, as shown below:

Treatments

• Chemotherapy
  • Cladribine (also known as 2CDA or Leustatin)
  • Etoposide
  • Vinblastine (Velban)

Society

Patients and families can gain support and educational materials from the Histiocytosis Association, or the Histiocytosis Research Trust. Information concerning histiocytosis and clinicians located in European countries may be found in many languages at the web portal of Euro Histio Net (EHN). This is a project funded by the European Union, coordinated by Jean Donadieu, APHP, Paris, France. Additional information about Erdheim–Chester disease can be obtained from the ECD Global Alliance.

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.