Erdheim-Chester Disease

Erdheim-Chester disease is a rare form of non-Langerhans cell histiocytosis. Its prevalence has increased significantly the past few years due to increased awareness about the disorder; about 1500 cases have been reported worldwide.

Erdheim-Chester disease (ECD) is a rare type of blood disease that belongs to the histiocytic disorders group, or histiocytosis. Histiocytosis involves the excessive production of histiocytes, which are a type of white blood cell. These cells, which normally help fight infection and injury, then gather in different organs and tissues and can result in a variety of symptoms, including organ failure.

The first two cases of ECD were reported by scientists Jakob Erdheim and William Chester in 1930. In 1972, Dr. Ronald Jaffe reported a third case and coined the name Erdheim-Chester disease (ECD).

ECD was previously considered an inflammatory or autoimmune disease, but was recognized as a blood cancer in 2016 by the World Health Organization. This was due to the discovery of cancer-causing DNA changes (mutations) in BRAF- and other genes in biopsy samples from most patients.

Erdheim-Chester is a disease that primarily affects adults, with an average age at diagnosis around 50 years. It can affect men and women. The disease-causing cells of ECD (histiocytes) can involve any organ system of the body from head to toe, but most commonly affect the long bones of the legs around the knees. Due to the wide variety of manifestations of ECD often mimicking other diseases, it is believed to be under-diagnosed.

While the exact cause of developing ECD is unknown, it is not considered a hereditary or contagious disease. The discovery of BRAF and other mutations has revolutionized the care of patients with ECD, resulting in targeted treatments that have the ability to improve patient survival.

The information on this page has been written and reviewed by the Histiocytosis Association Board of Trustees Scientific Committee and a member of the Histiocyte Society, and subsequently audited by patients and families to ensure enough information was captured. The most recent update to this page was in June of 2023.

Latest ECD Educational Webinar

Play Video


The signs and symptoms of ECD depend on the number and degree of organ involvement. The following section discusses the frequency of organ manifestations and corresponding symptoms experienced by patients with ECD. It is important to note that not all organ manifestations may result in symptoms. The signs and symptoms listed below may indicate disease involvement but are not necessarily diagnostic. The disease varies greatly from patient to patient, and some but not all of these symptoms may be present.

  • Bone (>90%): ECD involves the long bones around the knees in most cases, but can affect any other bone of the body. Most common symptom is bone pain in legs/knees, usually on both sides (bilateral)
  • Retroperitoneum (tissue surrounding kidneys and large blood vessels like aorta) and kidneys (50-60%): Can manifest as hairy growth around the kidneys affecting the kidney function or around the large blood vessels like the aorta. On CT scan of the body, this can appear as “hairy kidney” or “coated aorta”. The most common symptoms include abdominal or lower back pain, painful or difficult urination, kidney failure
  • Nervous System (including the brain (40-50%)): ECD can involve the parts of the brain that control balance and coordination (brainstem and cerebellum). It can also affect the spinal cord and nerves arising from it. Special imaging of the brain (MRI) is required to assess the involvement of nervous system by ECD. Symptoms include difficulty with coordination, difficulty difficulty maintaining balance, recurrent falls, slurred speech, behavior disorders, muscle weakness
  • Mood and memory difficulties (50-70%): ECD can cause difficulty with memory and mood in a large proportion of patients despite a completely normal MRI scan of the brain. Symptoms include mood lability, uncontrollable crying, anxiety, depression, difficulty remembering things
  • Pituitary gland and other hormone deficiencies (40-70%): Pituitary involvement most commonly presents as diabetes insipidus, and is often the first manifestation of the disease. Other pituitary hormone deficiencies that are commonly seen are growth hormone, gonadotropin, thyrotropin, and corticotropin. The pituitary hormone deficiencies may or may not be associated with abnormal pituitary MRI scan. Other hormones that can be deficient are thyroid, adrenal, and sex hormones (testosterone in men and estrogen in women).  Symptoms include excessive thirst and urination, fatigue, low libido, cold intolerance, weight gain
  • Heart (50-60%): Most common manifestation is infiltration of the heart muscle, specifically the right atrium (called as pseudotumor based on appearance on MRI scan of the heart). Occasionally can involve the outer covering of the heart (pericardium) leading to fluid accumulation (pericardial effusion). May involve the blood vessels supplying the heart (coronary arteries) or other blood vessels of the body. Symptoms include shortness of breath, fatigue, and swelling of feet, ankles, and lower legs
  • Lung and respiratory system (40-50%): Manifests usually as asymptomatic involvement of the coating of the lung (pleura). Can occasionally involve the sinuses as well. Symptoms include shortness of breath, dry cough, sinus congestion
  • Eyes (25-30%): ECD can cause accumulation of cells in the bony cavity of the skull that houses the eyeball (orbit), causing pressure and visual disturbances. Symptoms include pain and redness, bulging eyes, difficulty with vision including double vision
  • Skin/Eyelids (20-30%): Most commonly seen as yellowish-orange patches around the eyes called xanthelasmas. Rarely can involve other skin sites on face, neck, armpits, groin, or back. Symptoms include rash or soft, fatty, yellowish-orange bumps around the eyes
  • Liver, spleen, lymph nodes, and bone marrow (10%): Mostly asymptomatic involvement. ECD can be associated with other blood cancers such as myelodysplastic syndrome (MDS), myeloproliferative neoplasm (MPN), and chronic myelomonocytic leukemia (CMML). Usually asymptomatic, however can manifest as abnormally low or high blood cells on routine testing (CBC)
  • Additional Symptoms, regardless of organ involvement: fatigue, weight loss, low-grade fevers, night sweats, muscle and joint aches

Involvement of more than one system is not uncommon. While the long bones are the most frequently affected sites, more than 50% of patients have involvement in other parts of the body. Lung symptoms are due to progressive scarring and thickening of the lung tissue and can affect the ability of the heart to pump enough blood to the lungs and the rest of the body. Diabetes insipidus is believed to occur in 30% of patients. ECD of the heart causes problems when histiocytes accumulate in the valves or heart muscle and affect the heart’s ability to pump blood through the arteries.

It is important to remember that symptoms alone do not diagnose ECD. Thus, it is important to consult a physician to receive an appropriate workup and accurate diagnosis.

Diagnosis and Treatment

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 Guidelines are listed as "histiocytic neoplasms" and can be found on NCCN's website.

You can find consensus guidelines for the diagnosis and clinical management of Erdheim-Chester disease, here. It is encouraged that you share this with your physicians for reference.

On November 1st, 2022, Memorial Sloan Kettering Cancer Center (MSK) announced that the U.S. Food and Drug Administration (FDA) has approved the oral MEK inhibitor drug cobimetinib (Cotellic®) for the treatment of adult patients with the family of blood diseases known as histiocytic neoplasms (HN). These diseases include Erdheim-Chester disease, Rosai-Dorfman disease, and Langerhans cell histiocytosis. Cobimetinib is an oral inhibitor of MEK1 and MEK2, currently approved to treat melanoma. Gratitude and congratulations to the Principal Investigator of this study, Dr. Eli Diamond, neuro-oncologist and neurologist at MSK and Chair of the Scientific Committee for the Histiocytosis Association. We applaud the efforts of Dr. Diamond and the entire study team for this tremendous advancement. Read more here.

The diagnosis of ECD can be challenging and requires review of the biopsy of a tumor specimen in light of clinical and radiographic findings.

The classic diagnostic finding of ECD is abnormal imaging of the bones around the knee on a CT scan, PET scan, MRI, or a technetium bone scan. A PET CT scan (head to toes) is the preferred imaging study as it also allows to search for other sites of disease more accurately as compared with other radiographic tests. A biopsy of one of the affected sites from ECD using a needle or through surgery is usually conducted and reviewed by an expert pathologist under the microscope for features suggestive of ECD. One of these characteristics is the presence of foamy (bubbly) histiocytes with signs of inflammation.

A special test called immunohistochemistry is undertaken by using stains (dyes) that check for certain markers (antigens) in the tumor sample. The stains are called as “positive” if the tumor cells bind to the dye and are visible under the microscope, and negative if they do not. Altogether, the pattern of “positive” and “negative” stains help pathologists make a diagnosis from a biopsy sample. ECD cells are positive for the “markers” (stains) CD68 and factor XIIIa , and negative for CD1a. Langerhans cell histiocytosis, by contrast, is positive for CD1a. In addition, testing for mutations of the BRAF and other genes through special tests called as next generation sequencing (NGS) studies on the biopsy specimen or blood may be undertaken to help aid in the diagnosis or treatment. There are many hospitals, laboratories, or companies that perform NGS, and it is recommended to discuss with your doctor about which one to use for your case . In cases where the classic knee bone involvement or characteristic staining on biopsy is not present (seen less than 10% of the time), presence of a mutation in combination with other features mentioned above may lead to a diagnosis of ECD.

Baseline evaluation and testing

Once the diagnosis of ECD is made, detailed history, physical exam, and tests are undertaken to determine the extent of the disease, i.e., determining what organs are involved with the disease:

  • History: A detailed health history is undertaken including the onset and duration of symptoms, past illnesses, health and lifestyle habits, and medical conditions experienced by the family
  • Physical examination: Includes a detailed exam of the body to search for signs of ECD. A specialized neurological exam may also be undertaken to evaluate if ECD has affected the brain and the nervous system, and includes testing for reflexes, coordination, muscle strength, sensations, and memory
  • Blood tests:
    • Complete blood count with differential - to check for hemoglobin, platelets, and different types of white blood cells
    • Chemistries, including kidney and liver function tests: To evaluate the function of kidney and liver
    • C-reactive protein (CRP)- a marker of inflammation which can be elevated in ECD
    • Urine and serum osmolality, water deprivation test- to check if the ECD has affected the pituitary gland hormone that helps in concentration of urine is being secreted adequately
    • Other hormone tests – to assess whether ECD has affected endocrine organs like the pituitary gland, thyroid gland, or the adrenal glands
    • BRAF and other genetic mutation testing- to check for BRAF-V600E and other mutations in the blood
  • Tests on biopsy specimen:
    • Immunohistiochemistry: This test uses various types of dyes to find markers that can help in the diagnosis of ECD and differentiate it from other diseases. At times, BRAF-mutation testing can also be achieved relatively quickly using immunohistochemistry methods
    • Molecular testing for BRAF and other mutations: This test involves testing the tissue for changes in the BRAF gene, especially the BRAF-V600E mutation, as well as other mutations that can be driving the ECD (KRAS, NRAS, etc.). Some of these tests require sending the biopsy sample to a specialized laboratory that can take several days to weeks to result. Knowledge of these mutations can help with the diagnosis and treatment of ECD
  • PET (positive emission tomography) scan: To check for tumor cells in the body, a small amount of radioactive sugar is injected into a vein followed by taking pictures in a PET-scanning machine. The disease-causing cells look brighter than surrounding cells due to increased uptake of glucose
  • CT (compound tomography) scan: This is an x-ray that takes a number of detailed pictures of various organs and structures within the body, often conducted in combination with a PET scan. Dye may be injected into a vein or taken by mouth to make the images more clear
  • Bone scan: This is a type of x-ray that looks for rapidly dividing cells in the bones. A small amount of radioactive material is injected into a vein, collects in any abnormal parts of the bones, and is detected on a scanner
  • MRI (magnetic resonance imaging): A special type of scan that used magnetic waves to obtain detail pictures of various body parts. A substance called gadolinium may be injected into a vein to get clearer pictures
  • Ultrasound: This is a procedure where sound waves are used to create echoes and collect pictures of organs
  • Electrocardiogram: This is a tracking of the heart rate and rhythm
  • Echocardiogram: This uses sound waves to provide pictures of the heart in order to evaluate blood flow and heart function
  • Bone marrow aspiration and biopsy: This procedure involves suctioning of a small amount of bone marrow and taking a small piece of the bone by inserting a hollow needle in the hip bone
  • Specialist examinations: This may include a neurological examination to test ability to walk, muscle testing, coordination, etc.; other specialist visits or specific testing may be recommended by your physician


In many diseases or cancers, there is the concept of “staging” which refers to the extent or severity of the disease within the body (for example, “stage 4 lung cancer.” There is no standard staging system for ECD. The severity of the disease is determined by how widespread the involvement occurs outside of bone and whether internal organs are affected.


General principles of treatment

Most patients with ECD will require treatment at the time of diagnosis. In some patients who do not have any symptoms or any critical organ involvement like brain or heart, it is reasonable to pursue a “wait and watch” strategy for some period of time without treatment. In these cases, close monitoring by a specialist is needed, and may include repeated imaging studies like PET scan or CT scan.

Patients with ECD should have their treatment planned by a team of health care providers who are experts in the disease, including and not limited to the following:

  • Cancer specialist (hematologist/oncologist)
  • Hormone specialist (endocrinologist)
  • Autoimmune disease specialist (rheumatologist)
  • Lung specialist (pulmonologist)
  • Brain and nervous system specialist (neurologist)
  • Skin specialist (dermatologist)
  • Heart specialist (cardiologist)
  • Nephrologists (Kidney Specialists)
  • Ophthalmologist (Eye Specialist)
  • Psychologist and supportive care specialist
Treatments available for ECD

The treatment approach to ECD has evolved significantly due to discovery of mutations in the BRAF and other genes, leading to the successful use of targeted therapies in most cases. Treatments for ECD can be divided into two categories- targeted and conventional treatments. Patients may also consider enrolling in a clinical trial if available near them.

[conventional treatments chart]

Targeted Therapies: Targeted therapies include treatments that attack specific genes or protein in the cancer cells. Targeted therapies are likely required to be taken for a long time, as there is concern that the ECD will recur upon stopping the drug. There are different types of targeted therapies available for ECD:

  • BRAF-inhibitors (vemurafenib, dabrafenib, encorafenib): These drugs are typically used when there is presence of the BRAF-V600E mutation in the tumor cells. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment. The common side effects include skin reactions (rash or skin cancer), joint pains, and fatigue. Seeing a skin doctor regularly can help with management of these effects. Other less common but important adverse effect is abnormal heart rhythm or reduced heart function. Some patients on these drugs will get routine electrocardiograms and echocardiograms to monitor the effects on the heart. Some of the side effects may necessitate switching one type to BRAF-inhibitor to another.
  • MEK-inhibitors (cobimetinib, trametinib, binimetinib): These drugs are typically used when there is no BRAF-V600E mutation in the tumor cells. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment. Common side effects include skin rash, and patients may need to see a skin doctor for management. These drugs can also reduce the heart function, and sometimes an echocardiogram may be needed to monitor the effects on heart. Another notable side effect is changes in the layer of the tissue in the back of eye that senses light (retina) leading to blurry vision or loss of vision. It may be necessary to get regular eye exams while on treatment with these drugs.
  • Other inhibitors - mTOR inhibitors (sirolimus, everolimus), imatinib, sorafenib: These are less commonly used targeted therapies but can occasionally result in disease remission. These drugs are taken by mouth and the dose can vary based on side effects and response to treatment.  Side effects with mTOR inhibitors include abnormal cholesterol levels, lung inflammation (pneumonitis), and worsening of diabetes mellitus. Side effects with imatinib and sorafenib include rash, fatigue, and diarrhea.
Conventional Treatments:
  • Immunotherapy (interferon-alpha, peginterferon-alpha): Interferon was the most commonly used treatment for ECD before the introduction of BRAF and MEK-inhibitor therapies. Interferon is administered as an injection under the skin. Most common side effects that are experienced by the patients include fatigue, joint pain, flu-like symptoms, and depression.
  • Chemotherapy (cladribine, cytarabine, vinblastine, methotrexate): These drugs are given through the vein or mouth (methotrexate only). Chemotherapy works by slowing the growth of or killing rapidly dividing tumor cells. These drugs have the potential to weaken the immune system and can lead to infectious complications. Vinblastine can cause damage to the nerves leading to neuropathy, manifesting as numbness, tingling, or pain of fingers and toes. Cladribine can increase the risk of a particular type of pneumonia (pneumocystis pneumonia) so preventative antibiotics may need to be administered alongside.
  • Anti-cytokine therapy (anakinra, canakinumab, tocilizumab, infliximab): These treatments work by reducing the inflammation that is generated by tumor cells. Most commonly used drug is anakinra and is given as an injection under the skin. Common side effects include skin rash at the site of injection, headache, and sore throat. Tocilizumab and infliximab are given through the vein. Common side effects of these drugs include headache, nausea, stomach pain, and diarrhea.
  • Other treatments (steroids, surgery, radiation): Steroids may be given through the vein or by mouth to reduce inflammation from ECD. The side effects include weight gain, stomach upset, sleep disturbances, and increased blood sugars. Surgery may be used to remove ECD lesions or to reduce the pressure from a large lesion behind the eye. Occasionally, radiation therapy using high energy x-rays or protons may be used to kill tumor cells. The side effects of radiation can depend on the site of radiation and the amount of normal tissue exposed to the radiation.

Monitoring on Treatment

Once treatment is initiated, patients will likely need monitoring for assessing the response to therapy and also management of side effects of treatments. Some of the tests that may be undertaken include:

  • Physical exam, including neurological exam
  • Skin exams in patients on BRAF- and MEK-inhibitor treatments
  • PET scan to check for reduced brightness and size of the tumor sites
  • Additional imaging studies (CT, MRI) may be undertaken based on organs involved at diagnosis. Imaging (PET, CT, MRI) is usually repeated every few months and can be variable for each patient
  • Blood tests to assess for changes from the disease or the treatments
  • Hormone evaluation and treatment with the help of an endocrinologist

Treatment of Relapsed ECD

If the tumor grows back after treatment, it is called as relapsed disease. In such cases, one of the other targeted or conventional treatments than used previously may be utilized. In some cases, a repeat biopsy of tumor cells may be needed for confirmation of diagnosis and mutation testing. If a clinical trial is available, that may be a consideration as well.

Supportive Care

Despite improvement in treatments, patients with ECD struggle with many symptoms such as extreme tiredness, body pain, depressed mood, anxiety, and memory difficulty. In many cases, getting additional input from psychology, supportive/palliative care, psychiatry, and pain specialists may be helpful. Leading a healthy lifestyle (exercise, balanced diet) may help improve some of these symptoms in addition to medications.


The prognosis of ECD has continued to improve with introduction of newer treatments and early diagnosis. That has allowed ECD to become more of a chronic disease; however, at this point it is still considered incurable. It is important for patients to continue to follow up with their healthcare provider to ensure no complications such as second cancers or side effects of treatment develop. If there is development of any new symptoms, it is critical to notify the healthcare team to catch these problems in a timely manner.


ECD Referral Care Centers and Specialists

ECD Referral Care Centers and disease specialists are available to treat patients and/or provide consultation to local treating physicians when patients cannot travel.  The Erdheim-Chester disease Global Alliance (ECDGA) and the Histiocytosis Association maintain a list of such centers and physicians at the websites below:

Understanding Histiocytosis

The Histiocytosis Association collaborates with leading experts to create educational materials for ECD and other histiocytosis. These can be on our Overview of Histiocytic Disorders page.

Additionally, there are numerous opportunities to receive education on disease and connect with experts through online lectures (webinars) and in-person patient and family events. To stay connected with all the updates, you can register/subscribe to receive emails from the Histiocytosis Association and the Erdheim-Chester disease Global Alliance.

How Can You Help?

Take Part in Research

People are needed for clinical studies that can help find effective treatments and improve for patients with ECD. These studies can be either interventional (to find effective treatments), translational (to collect samples like blood, saliva, tumor for finding new targets for treatment), or observational (to study health effects of the disease or treatments). There are two ongoing registries for patients with ECD and other histiocytosis, whereby the patient information is stored for research - the ECD patient registry and International Rare Histiocytic Disorders Registry. There is also an open study into the survivorship of patients impacted by histiocytic disorders. Email us at or give us a call at 856-589-6606 to learn more. You can also ask your doctor about how to participate in such studies or find more information on the our clinical trials and registries page.

Donate to Research

The Histiocytosis Association and ECD Global Alliance support vital research and education to discover the cause and improved treatments for patients with ECD. For more information on how you can donate, visit our donation page or learn about other ways to give.


What Do I Do Now?

A new diagnosis of a histiocytic disorder can bring feelings of being overwhelmed, bewildered, scared, angry, sad, disappointed, helpless, and sometimes even feelings of guilt.  It is a time filled with unknowns, change, and new people and situations.  Most parents feel ill-equipped to understand what is happening to their child and how to navigate through the illness to recovery.  There are, however, strategies and resources that can help you, your child, and other family members get through the uncertain times that lie ahead. One step at a time, you can gather information, create a support system, learn how to cope with stress, and become a strong advocate for your Histio Warrior as part of the medical team. The following tips and suggestions are provided to help guide you through this journey toward your Histio Warrior's good health.

Printable Fact Sheets

Learn more about the different types of histiocytic disorders from these helpful fact sheets. Printing these for family and friends is a quick and easy way to teach them about the disease. More extensive information can be found in the Disease Information section of our website.

Choose from the following Fact Sheets:

Histiocytic Disorders Overall FAQ