Erdheim-Chester disease (ECD) is a rare non-Langerhans cell, non-familial multisystemic histiocytosis, with widespread manifestations and of highly variable severity.
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Epidemiology
Erdheim-Chester disease is a rare, non-inherited disease of middle age with a slight male predominance 6.
Clinical presentation
Patients may present with a variety of symptoms, ranging from focal neurological deficits to multiorgan failure 5. The most common presenting symptom is bone pain. However, patients may also present with focal neurological deficits, exophthalmos, retroperitoneal fibrosis, diabetes insipidus, and dyspnea due to the variably extensive extraskeletal involvement of the disease.
Pathology
Erdheim-Chester disease is a systemic lipogranulomatous disorder with infiltration by lipid-laden histiocytes (foamy macrophages), Touton giant cells, and a variable amount of background fibrosis 2. In contrast to Langerhans cell histiocytosis (LCH), no S-100 nor CD1 are detected 1, but CD68 is positive 10. It is associated with BRAF V600E mutations 14-16.
Both Erdheim-Chester disease and Langerhans cell histiocytosis (LCH) may coexist, and cases of double infiltration have been reported 10.
Radiographic features
Musculoskeletal involvement is most common, with multifocal extraskeletal involvement seen in 30-50% of patients 1,2.
Skeletal involvement
bilateral, symmetric metaphyseal and diaphyseal sclerosis 1,2
increased uptake on Tc-MDP bone scan 7
cortical thickening
Visceral
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lung (see: pulmonary manifestations of Erdheim-Chester disease)
can appear similar to Langerhans cell histiocytosis with predominantly cystic disease, septal thickening and preserved lung volume
chest radiographs will often show interstitial edema pattern (interlobular septal thickening) with cardiomegaly and pleural effusions that do not respond to diuretics
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often involved
usually asymptomatic 1
hairy kidney sign: irregular symmetric infiltration of the bilateral perirenal and posterior pararenal spaces 11
coated aorta sign: periaortic soft tissue 11
inferior vena cava and pelvic ureters are typically spared, which are useful cross-sectional imaging findings for differentiation of retroperitoneal Erdheim-Chester disease from retroperitoneal fibrosis 8
skin
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retro-orbital tissue
retrobulbar masses that can cause proptosis and motility impairment 13
retrograde extension along the optic nerve to the hypothalamus may explain the distribution of brain involvement 4
heart, pericardium and aorta 2
Intracranial
Intracranial involvement of the dura, brain and pituitary are rare 3:
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dural accumulations may mimic meningiomas, with enhancing soft tissue masses
T2 signal characteristics are somewhat different, as the accumulations in Erdheim-Chester disease are hypointense 3
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brain
most commonly affecting the pons and cerebellum 14
can also affect the hypothalamus 3,14
intraparenchymal masses appear non-specific 10
pituitary infundibulum 14: presenting with diabetes insipidus
Treatment and prognosis
Corticosteroids, radiotherapy and chemotherapy have all been used but with little effect, with some patients relentlessly progressing 1. In patients with BRAF V600-mutant Erdheim-Chester disease, BRAF inhibitors, such as vemurafenib, can be effective 15,16. Surgical or percutaneous intervention for hydronephrosis, orbital or meningeal involvement is useful for symptomatic local disease.
Pulmonary fibrosis and cardiac failure are the most common causes of death 2. Given the small volume of published data, mortality rates are unclear but may be as high as 60% 2.
History and etymology
It was first described in 1930 as "lipid granulomatosis" by Jakob Erdheim (1874-1937), an Austrian pathologist, and William Chester (1903–1974), an American pathologist 9,12.
Differential diagnosis
The differential diagnosis for Erdheim-Chester disease is very dependent on location although some entities will be considerations in most locations (e.g. lymphoma).
Intracranial
The differential for intracranial involvement is that of other causes of dural masses including: