Understanding Histio

Overview of Histiocytic Disorders

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.

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This group of histiocytic disorders 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:

Dendritic Cell Disorders

The most common disease in this group is Langerhans cell histiocytosis (LCH). Also included in this group are more rare diseases, pulmonary Langerhans cell histiocytosis (PLCH), juvenile xanthogranuloma (JXG) and Erdheim-Chester Disease (ECD).

Macrophage Cell Disorders

This group includes primarily hemophagocytic lymphohistiocytosis (HLH) and Rosai-Dorfman Disease (RDD).

Malignant Cell Disorders

This group includes certain kinds of leukemia and malignant tumors.

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 RDD.

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.

NCCN Histio Clinical Guidelines

NCCN Publishes Guidelines for LCH, ECD, and RDD

March 1, 2021:  We are excited to share that the National Comprehensive Cancer Network® (NCCN®) - an alliance of leading cancer centers - announced the publication of new NCCN Guidelines® for histiocytosis. These clinical practice guidelines provide the latest evidence and expert-consensus for diagnosing and treating the three most common forms of histiocytosis in adults: Langerhans cell histiocytosis (LCH), Erdheim-Chester Disease (ECD,) and Rosai Dorfman Disease (RDD). Although the guidelines are focused on adult patients, there may be insight for pediatric physicians as well.

The NCCN is comprised of 30 leading cancer centers that are dedicated to improving patient lives through research and education, and the development of valuable resources to help physicians, researchers, patients, and families. In a recent press release by NCCN, the Histiocytosis Association was honored to be able to share our excitement and support, alongside the ECD Global Alliance team and others.

"The Histiocytosis Association appreciates the dedication of all those involved at the NCCN for developing and publishing guidelines for three of the histiocytic disorders,” said Deanna Fournier, Executive Director, Histiocytosis Association. “As with all rare diseases, early diagnosis and awareness of the proper course of treatment has a very positive impact on patient outcomes; having access to the most up-to-date information at the ready will enable physicians around the world to continue to provide the best care to adults and children impacted by histiocytosis. We look forward to sharing the guidelines with our community."

The NCCN Guidelines can help patients, families and physicians access the latest information about symptoms, diagnosis, treatment, and more. They are useful tools when seeking approvals for coverage of drugs and therapies. They are available to access or download globally with a free NCCN account through their website or mobile app, which many physicians actively use in their practices. The guidelines are updated at least once a year and can be accessed at any time. You can view the published guidelines on NCCN’s website listed as “histiocytic neoplasms”. If using the guidelines outside of the United States, be sure to consult local healthcare providers about availability and coverage in other regions.

We encourage you to share these guidelines with your medical team.

If you have any questions, please do not hesitate to contact us. We are thrilled to be able to support the advancements of resources like these and look forward to sharing more with you in the coming weeks.

Want to learn more about the NCCN and the important work they do? Click here.

(Guidelines are listed as "histiocytic neoplasms")