A group of rare disorders characterized by proliferation and accumulation of histiocytes.

Annual incidence of less than five cases per million population.

These histiocytic diseas3 originate from cells of the myeloid lineage and primarily include Erdheim-Chester disease, Langerhans cell histiocytosis (LCH) and Rosai-Dorfman disease (RDD) , but several other processes.

Of unknown etiology.

Subclassified as LCH and RDD

Maybe seen in all age groups.

About 500 cases of ECD had been reported.

These neoplasms may present as focal or diffuse multiple organ disease.

The disease spectrum varies from incidental lesions noted on imaging studies to severe illness arising from severe organ dysfunction.

May behave like a neoplasm, and 54% of patients have a BRAF V600E mutation.

Recurrent activating mutations in mitogen-activated protein kinase/extracellular signal regulated kinase pathways occur in more than 90% of patients demonstrating clonal origin.

In ECD lower extremity bone pain is one of the most common presenting symptoms, occurring in approximately 50% of patients.

Bilateral symmetrical osteosclerosis around the knees is coming at about 95% and is pathognomonic of ECD.

In ECD involvement of the axial skeleton and the small bones of the feet can  be seen, 47% and 9%, respectively.

ECD treatment options include corticosteroids, vinca alkaloids, anthracyclines, cladribine, alpha interferon, Imatinib, anakinra, and infliximab.

Adult LCH commonly involves bones and maybe a bone limited disease or component of multi system disease, 38% and 66%, respectively.

The skull is the most commonly involved, followed by the axial and proximal appendicular skeleton.

CNS  involvement in histiocytic neoplasms maybe associated with increased risk of mortality.



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