About ECD
The ECDGA YouTube playlist includes 11 videos featuring medical professionals who explain what ECD is, how it is diagnosed, and current treatment approaches.
What is Erdheim-Chester Disease?
Overview
Erdheim-Chester Disease (ECD) is an extremely rare blood cancer that can affect many different organs of the body. It is characterized by excessive production and accumulation of specific cells whose normal functions are to fight infections and eliminate foreign bodies. These cells, called histiocytes, infiltrate the loose connective tissue within body organs and cause inflammation. As a result, this tissue becomes thickened, dense, and scarred, or “fibrotic.” If the disease is not controlled, organ failure can occur. In some patients, ECD may have a relatively mild course involving a limited number of organs. In contrast, in others, the disease can be more aggressive and may affect multiple organs, including, but not limited to, the bones, skin, heart, kidney, and brain. For this reason, care is usually provided by a team that may include hematologists, oncologists, endocrinologists, neurologists, cardiologists, ophthalmologists, and other specialists. This team-based approach helps ensure that all organ systems are monitored and treated appropriately.
Who is typically affected by ECD?
The majority of ECD patients are typically diagnosed between the ages of 40-70 years, although occurrences in children have been infrequently reported. ECD can affect both men and women, although approximately 70% of reported cases occur in men and 30% in women.
What causes ECD?
The exact cause of ECD is unknown. However, in 2016, the World Health Organization (WHO) categorized ECD as a type of blood cancer called histiocytic neoplasm. This recognition was due to the discovery of cancer-causing DNA changes (mutations) in the ECD tissues, specifically in the genes of the mitogen activating protein kinase (MAPK) pathway, including BRAF, KRAS, MAP2K1, NRAS, etc. genes. The most common mutation is BRAF V600E, which is identified in about 50-60% of ECD cases. These mutations are not believed to be inherited through DNA from parents but are acquired during life (somatic) and occur in cancer cells or blood cells. Therefore, they are not considered transmissible through generations; ECD does not “run in families.” In addition to MAPK pathway mutations, several other mutations have been discovered in ECD in recent years. These include mutations in genes such as CSF1R, ALK, and PIK3CA. Although less common, they affect similar pathways that control cell growth and inflammation and further support that ECD is a cancer of the immune system. Some of these mutations also have potential targeted treatments, but these therapies are still being studied and are not yet standardized.
What issues does ECD cause?
ECD can affect nearly all body parts, although the most common are the long bones of the legs and arms, skin, the tissues behind the eyes, lungs, brain, pituitary gland, the tissue around the kidneys and the ureters, abdominal cavity, the heart, blood vessels, and adrenal glands. Involvement of other organs occurs more rarely. The specific organs involved can vary; however, the most common presentation seen in over 90% of patients with ECD is the involvement of leg bones around the knees. The number of affected organs can vary between individuals, making the clinical presentation and aggressiveness differ greatly between patients.
In some patients, ECD occurs together with another related disease such as Langerhans Cell Histiocytosis (LCH) or Rosai-Dorfman Destombes Disease (RDD). This combination is known as “mixed histiocytosis”.
Brief History
There have been a very limited number of published cases of ECD in the world since it was first described in 1930 by the Austrian pathologist Jakob Erdheim and the American pathologist William Chester. Since ECD is so rare and is not discussed in common medical textbooks, many doctors have never heard of it. It is also considered difficult to diagnose. For these reasons, most feel the disease is underdiagnosed. However, in recent years, as awareness grows, there seems to be an increasing number of documented ECD diagnoses. Moreover, treatments have improved dramatically with the discovery of MAPK pathway mutations, leading to the US FDA approval of two targeted drugs, vemurafenib and cobimetinib, for patients with ECD.
Current Efforts to learn more
Most published articles on ECD were initially anecdotal (describing small numbers patients without thorough detail) in nature because studies were historically extremely difficult due to the small and geographically dispersed ECD patient population. However, a significant change began when patients and caregivers joined together to form the ECD Global Alliance. As part of this effort, ECD Referral Care Centers have been formed to provide comprehensive care for patients with ECD. There are several ongoing studies ranging from the discovery of new treatments to the improvement of symptoms and survivorship experience with this disease. The World Health Organization’s declaration of ECD as a blood cancer has enabled ECD better visibility, with improved opportunities to educate patients and their medical providers. Further, the American National Comprehensive Cancer Network has issued treatment recommendations and guidelines for ECD. This has made it possible for many medical providers to familiarize themselves with treatment strategies for ECD more easily.
What is the prognosis?
The prognosis for ECD is variable and depends mainly on the extent and distribution of the disease. It ranges from asymptomatic bone lesions to multi-systemic life-threatening forms. Due to the discovery of targeted therapies, the prognosis of ECD has improved significantly, both in terms of mortality (the rate of deaths) and morbidity (the rate of illness). It is important to note that some patients with ECD have been living high-quality lives for decades. However, while targeted therapies like vemurafenib and cobimetinib have made it possible to control ECD, they are not curative in nature. Nevertheless, it is important to note that targeted therapies control disease in almost all patients, resulting in ECD being treated as more of a chronic disease for many. Patients often struggle with the side effects of treatment and/or long-term effects of their disease. Despite these challenges, the focus has shifted from preventing death and disability to maximizing patients’ quality of life over the last decades. The scientific field is evolving day by day, and more effective treatment strategies and guidelines to monitor patients effectively are hoped to be available in the near future.
Possible Specialists to Include on the ECD Patient Team
- Hematologist / Oncologist
- Endocrinologist
- Nephrologist
- Dermatologist
- Ophthalmologist
- Neurologist
- Pathologist
- Pulmonologist
- Cardiologist
- Radiologist
- Interventional Radiologist
- Counseling Services (i.e., Psychiaty/Psychology/Social work
- Physical Therapist/Physiotherapist
Next> Symptoms
Last Updated: 03/17/2026