Histiocytosis: Langerhan and Non Langerhan

Histiocytic disorders are currently identified by their component cells. It can be divided into Langerhan and non-Langerhans cell histiocytoses based on the latest revised classification system of histiocytoses and neoplasms of macrophage-dendritic cell lineages.

Langerhans cell histiocytosis (LCH) is a rare clonal disease characterized by the proliferation of CD1a-positive immature dendritic cells. It is known as a great imitator as its clinical presentation is highly variable and may mimic common childhood diseases like seborrheic dermatitis, diaper dermatitis, arthropod bites, skin infections and many more. It can present as isolated, self-healing skin and bone lesions to life-threatening multi-system disease that progresses rapidly.

The non-LCH are benign proliferative disorders which clinically can be divided into three major groups—those that predominantly affect the skin, those that affect the skin but have a systemic component as a major part of the disease, and those that primarily involve extracutaneous sites. The common types seen in children such as Juvenile xanthogranuloma (JXG)and benign cephalic histiocytosis will be discussed in detail.