The variable presentation and natural history of Langerhans cell histiocytosis.

Langerhans cell histiocytosis is not a well defined or predictable disease. Instead, it is a spectrum of disorders of unknown etiology that vary widely in presentation and natural history, but have in common the proliferation of histiocytic cells and infiltration of these cells into normal tissues. Although the lesions of Langerhans cell histiocytosis consist primarily of histiocytes, eosinophils are a prominent feature in some lesions. Lesions may develop in any tissue, but bone, skin and lymph nodes are the most commonly affected, and more than 75% of patients have skeletal lesions. Bone lesions caused by Langerhans cell histiocytosis vary from focal sharply defined areas of bone lysis to diffuse osteopenia and can resemble lesions caused by a wide variety of metabolic, infectious and neoplastic diseases. The natural history varies from a benign disorder that resolves spontaneously to a progressive fatal disease. In general, the younger the individual at the time of onset of the disease, the poorer the prognosis and the more extensive the disease. Treatment may include surgery, chemotherapy and radiation therapy, depending on the extent and severity of the disease.