Langerhans cell histiocytosis is a disease which results from accumulation or proliferation of a clonal population of cells with the phenotype of Langerhans cells arrested at an early stage of activation that are functionally defi cient. The etiology and pathogenesis of the disorder are still unknown. There are ongoing investigations to determine whether it is a reactive or a neoplastic disease...

A 13-year-old girl developed a non-pruritic pityriasis rosea-like rash, which did not respond to topical corticosteroids or UV therapy but persisted for 2 years. The lymphohistiocytic infiltrate in the upper dermis showed mononuclear cells immunoreactive with S100, CD68, factor XIIIa and CD1a. Electron microscopic evaluation of these cells demonstrated lamellated dense bodies but no Birbeck gra...

An unusual case of an isolated histioproliferative lesion arising from the suprasellar region is described. The presence of lymphophagocytosis suggested that this represented an extranodal intracranial form of sinus histiocytosis with massive lymphadenopathy.

Histiocytoses are clonal disorders diseases derived from the monocyte-macrophage lineage. The Erdheim–Chester Disease (ECD) and Langerhans Cell Histiocytosis (LCH) may occur in association with overlapping clinical, histopathological molecular features, harboring somatic MAP2K1 mutations more than 50% of patients. BRAF MEK inhibitors have shown to be efficacious ECD LCH, including responses pat...