Histiocytosis is a general name for a group of disorders or "syndromes" that involve an abnormal increase in the number of specialized white blood cells that are called histiocytes.
Recently, new knowledge about this family of diseases has led experts to develop a new classification. Five categories have been proposed:
- L group -- includes Langerhans cell histiocytosis and Erdheim-Chester disease
- C group -- includes non-Langerhans cell histiocytosis that involves the skin
- M group -- includes malignant histiocytosis
- R group -- includes Rosai-Dorfman disease
- H Group -- includes hemophagocytic lymphohistiocytosis
This article focuses only on the L group, which includes Langerhans cell histiocytosis and Erdheim-Chester disease.