histiocytosis

In medicine, histiocytosis is an excessive number of histiocytes,^[1] that is, an excessive number of tissue macrophages, and is typically used to refer to a group of rare diseases which share this as a characteristic. Occasionally and confusingly, it is sometimes used to refer to individual diseases.

The histiocytes may attack skin, bone, muscles, and other important organs, including the liver, lung, spleen, and hematopoietic system. The disease is somewhat similar to cancer, and treatment often involves radiation and chemotherapy.

According to the Histiocytosis Association of America, 1 in 200,000 children in the United States are born with histiocytosis each year.^[2] HAA also states that most of the people diagnosed with histiocytosis are children under the age of 10. The University of California, San Francisco, states that the disease usually occurs from birth to age 15.^[3]

Histiocytosis (and malignant histiocytosis) are both important in veterinary as well as human pathology.

Presentation

Histiocytosis is frequently associated with diabetes insipidus, even after several years of diagnosis and successful therapy.

Classification, and relationships to other conditions

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.^[4][5]. However, the classifications in ICD10 and MeSH are slightly different, as shown below:

Types of LCH have also been known as "Eosinophilic Granuloma", "Hand-Schuller-Christian Disease", "Letterer-Siwe Disease", and "Histiocytosis X". (See Langerhans cell histiocytosis for details).

Alternatively, histiocytoses may be divided into the following groups:^[6]:714-724

• X-type histiocytoses
• Non-X histiocytoses

Common treatments

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

Organizations

Patients and families can gain some support by contacting patient organisations such as the Histiocytosis Association of America, which has several stable and proven treatment protocols available only for physicians^[7], or the Histiocytosis Research Trust.

References