Histiocytic disorders are a group of diseases that occur when there is an over-production of white blood cells known as histiocytes that can lead to organ damage and tumor formation. This group is made up of a wide variety of conditions that can affect both children and adults. In order to reduce confusion, in 1987, the Histiocyte Society classified these disorders into three groups based on the types of histiocyte cells involved:
The classification of these disorders has created a common name and language for the different histiocytic disorders. Guidelines for diagnosis, treatment, and follow-up of the histiocytic disorders have been created by the Histiocyte Society. With the new system of classification, cooperative international clinical studies have been created for LCH and HLH. In these studies, patients are registered by their physicians to participate, and valuable information is gathered on all of the patients who are registered. The purpose is to evaluate information in order to improve current treatment options and outcomes, obtain information on new treatments, and provide direction for what research needs to be undertaken in the future. Those patients who are enrolled in clinical trials can benefit from the latest information about the treatment and care of the histiocytic disorders, as well as contribute to the international effort to improve outcome. Over the past 15-20 years, a vast amount of research, much of which has been funded by the Histiocytosis Association, has improved the understanding of LCH and HLH, as well as the more uncommon histiocytic disorders such as JXG, ECD and RD.
Each of these diseases is very different, and the symptoms, rate of occurrence, diagnostic testing, and treatments vary widely. For more information about a particular histiocytic disorder, please see the corresponding pages.