Histiocytosis

disease involving clonal proliferation of Langerhans cells

uncommon hematologic disorder seen more often in children than in adults

In medicine, histiocytosis is an excessive number of histiocytes (tissue macrophages), and the term is also often used to refer to a group of rare diseases which share this sign as a characteristic. Occasionally and confusingly, the term histiocytosis is sometimes used to refer to individual diseases.

rare disease

multifocal, unisystem form of Langerhans-cell histiocytosis. There is involvement of multiple sites in one organ system, most frequently the bone. Patients are usually young children presenting with multiple destructive bone lesions