What's Erdheim-Chester disease?
Erdheim-Chester disease (ECD) is a rare histiocytic neoplasm: clones of immune cells called histiocytes accumulate and infiltrate tissues throughout the body. It is now understood as a clonal myeloid disorder driven by acquired (somatic) mutations in the MAPK signalling pathway, most often BRAF V600E, present in more than half of cases. These mutations arise after conception in blood-precursor or tissue cells, so ECD is not inherited and is not passed to children. This entry confirms a somatic BRAF V600E driver, the basis for its targeted treatments.
| Also indexed as | ORPHA:35687, MONDO:0018153 |
|---|---|
| Features mapped | 13 |
| Treatments mapped | 3 |
| Published sources | 9 |
| Last reviewed | 2026-08-04 |
Signs and symptoms
Abnormal metaphysis morphology
Erdheim-Chester disease typically hardens and thickens the long bones of the arms and legs (sclerotic bone lesions). This bone change is one of the disease's characteristic findings.
Abnormal cerebellum morphology
Erdheim-Chester disease can involve the brain, and the cerebellum (the part that coordinates movement and balance) is a region that is frequently affected. Imaging scans often show abnormal activity there.
Abnormal pericardium morphology
Erdheim-Chester disease can affect the pericardium, the sac around the heart, causing it to stiffen (restrictive pericarditis). This is one of the disease's typical findings.
Diabetes insipidus
Infiltration around the pituitary commonly leads to diabetes insipidus, in which the body cannot concentrate urine, leading to heavy urination and thirst. It is frequently one of the earliest signs.
Fatigue
When Erdheim-Chester disease causes symptoms, fatigue is one of the most common. It often appears alongside bone pain.
Bone pain
Bone pain, typically symmetric and in the legs, is among the most common symptoms and can persist for years before diagnosis.
Visual impairment
Erdheim-Chester disease can affect vision, both through masses behind the eye and through involvement of the brain and pituitary region. Visual disturbances are among the more common neurological signs of the disease.
Proptosis
Erdheim-Chester disease can push the eyes forward in their sockets, a feature called exophthalmos (also known as proptosis). It is among the findings frequently seen in the disease.
Xanthelasma
Erdheim-Chester disease often produces yellowish, fatty deposits in the skin around the eyes, called xanthelasma-like lesions. These are among the features frequently seen in the disease.
Retroperitoneal fibrosis
Fibrous, infiltrating tissue can wrap the structures at the back of the abdomen (retroperitoneal fibrosis), classically sheathing the kidneys (the 'hairy kidney' appearance) and the aorta, which can obstruct the ureters or compromise blood vessels.
Increased bone mineral density
A near-defining feature is symmetric hardening (sclerosis) of the long bones of the legs and arms, seen as increased bone density on X-ray or bone scan; it is often accompanied by bone pain.
Coated aorta (periaortic infiltration)
Erdheim-Chester disease can wrap a sheath of abnormal cells around the aorta, the body's main artery. On a scan this looks like a 'coated aorta' and is one of the signs doctors look for. It reflects cardiovascular involvement that needs monitoring.
Hairy kidney (perinephric infiltration)
Erdheim-Chester disease often infiltrates the fatty tissue around the kidneys, giving them a fuzzy outline on scans known as the 'hairy kidney' sign. It is a characteristic clue to the diagnosis and a marker of how far the disease has spread.
How it is diagnosed
Erdheim-Chester disease
Diagnosed using: BRAF V600E mutation testing.
“Erdheim-Chester disease (ECD) is a rare form of non-Langerhans-cell histiocytosis, associated in more than 50% of cases to BRAF(V600E)…”
Erdheim-Chester disease
Diagnosed using: immunohistochemistry (CD68+/CD1a-/S-100-).
“…positive staining for CD68 and negative staining for S-100 protein and…”
Erdheim-Chester disease
Diagnosed using: FDG-PET and MRI imaging.
“FDG-PET and MRI frequently show skeletal and cerebellar uptake in…”
Treatment and management
What the research describes, not a recommendation. Treatment decisions belong with your clinician.
This covers treatments that appear in the published research mapped here. Investigational and experimental therapies are not included, so their absence is a boundary of this map, not a sign they do not exist.
vemurafenib
Vemurafenib is a targeted medicine that blocks the BRAF protein. It was the first targeted therapy approved for Erdheim-Chester disease in people whose disease carries a BRAF-V600 mutation.
Used to help with: Erdheim-Chester disease.
“Anecdotal responses to vemurafenib, a BRAF-V600E inhibitor, have been reported in a few cases of LCH and Erdheim-Chester disease.”
trametinib
Trametinib is a MEK inhibitor that acts one step downstream of BRAF in the same MAPK pathway. It is an option for ECD, including cases without a BRAF V600E mutation, and is often effective at low doses.
Used to help with: Erdheim-Chester disease.
“To assess the efficacy and safety of the MEK inhibitor trametinib, we retrospectively analyzed the outcomes of 26 adult…”
interferon-alpha
Interferon-alpha has historically been used as a first-line treatment for Erdheim-Chester disease, and some people improve on it.
Used to help with: Erdheim-Chester disease.
“…interferon-α was considered as our first line treatment of…”
What changes how it shows up
Carrying the genetic change is not the whole story. The factors below are described in the research mapped here as changing whether, or how strongly, the condition appears. They modulate how the genotype is expressed; they do not, on their own, cause or cure it.
BRAF V600E mutation / MAPK pathway activation
Erdheim-Chester disease is driven by activating mutations in the MAPK (RAS-RAF-MEK-ERK) growth-signaling pathway, most often a BRAF V600E mutation. This discovery reclassified the disease as a neoplastic disorder and opened the door to targeted therapy.
Described as modulating: Erdheim-Chester disease.
“…rare histiocytosis that was recently recognized as a neoplastic disorder owing to the discovery of recurrent activating MAPK (RAS-RAF-MEK-ERK) pathway…”
How to read the evidence labels
Where this comes from
This guide is built from 9 published source(s). Every claim above links back to one of them. Click any source ID to read the original on PubMed.
Take it further
Printed, source-linked documents built from this condition's graph — ready to bring to an appointment or attach to a coverage request. Every claim carries its published source, the same as this guide.