Tags: Disease.
In medicine histiocytosis refers to an excessive number of histiocytes (tissue macrophages) and is typically used to refer to a group of rare diseases which share this as a characteristic. Occasionally and confusingly the term histiocytosis is sometimes used to refer to individual diseases.According to the Histiocytosis Association 1 in 200000 children in the United States are born with histiocytosis each year.