Histiocytoses

The histiocytoses encompass a group of diverse disorders characterised by the accumulation and infiltration of variable numbers of monocytes, macrophages, and dendritic cells in the affected tissues. Such a description excludes diseases in which infiltration of these cells occurs in response to a primary pathology. The clinical presentations vary greatly, ranging from mild to life threatening including multisystem Langerhans cell histiocytosis, and leukaemia.

This chapter provides a brief overview of the histiocytoses and is set out as follows:

The histiocytoses are classified as follows:

Class I histiocytosis

• Langerhans cell histiocytosis

Class IIa histiocytosis - histiocytosis involving cells of the dermal dendrocyte lineage, including:

• Dermatofibroma
• Juvenile xanthogranuloma
• Xanthoma disseminatum  

Class IIb histiocytosis - histiocytosis involving cells other than Langerhans cells and the dermal dendrocyte lineage, including:

• Multicentric reticulohistiocytosis 

Class III histiocytosis - malignant histiocytoses, including:

• Monocytic leukaemia
• Malignant histiocytosis

The conditions listed above represent just a few of the histiocytoses, over 20 different conditions have been described. Other than dermatofibromas, the other conditions are uncommon / rare, and so generally fall out of the scope of this website. However, more information can be found on some of these conditions, highlighted in the related chapters.