The histiocytic disorders are clinically heterogeneous disorders that result from an abnormal proliferation of histiocytes that are either
Dendritic cells (antigen-presenting cells)
Monocyte-macrophages (antigen-processing cells)
Classifying histiocytic disorders is difficult (see table Histiocytic Disorders) and has changed over time as an understanding of the biology of these cells has evolved (1). Langerhans cell histiocytosis is the most common histiocytic disorder. There are other rare histiocytic disorders such as Erdheim-Chester disease and juvenile xanthogranuloma, some of which are now considered variants of Langerhans cell histiocytosis (2).
General references
1. Emile JF, Abla O, Fraitag S, et al: Revised classification of histiocytoses and neoplasms of the macrophage-dendritic cell lineages. Blood 127(22):2672–2681, 2016. doi: 10.1182/blood-2016-01-690636
2. Höck, M., Zelger, B., Schweigmann, G. et al: The various clinical spectra of juvenile xanthogranuloma: Imaging for two case reports and review of the literature. BMC Pediatr 19, 128, 2019. doi: 10.1186/s12887-019-1490-y
