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A Pictorial Review of Paediatric Histiocytic Disorders in the Head and Neck

Objectives: Histiocytoses are a group of rare disorders characterised by an overproduction and accumulation of histiocytes - a subtype of white blood cell comprised of macrophages, dendritic cells or monocyte-derived cells - resident in various tissues and organs1,2.

Langerhans cell histiocytosis (LCH) has long been the publicist for histiocytic disorders and remains a familiar entity to paediatric and musculoskeletal radiologists. However more than 100 different subtypes have been described with wide ranging clinical manifestations and histologies. Recently a revised classification system has been employed consisting of five disease groups1 - (1-L) Langerhans-related, (2-C) cutaneous and mucocutaneous, (3-R) Rosai-Dorfman, (4-M) malignant histiocytoses, and (5-H) haemophagocytic lymphohistiocytosis (HLH).   Methods: Head and neck involvement is relatively uncommon. Pictorial review includes a catalogue and comprehensive review of pertinent radiological findings of rare paediatric histiocytic disorders involving the head and neck region. This includes imaging examples and descriptions of LCH (figures 1,2), Erdheim-Chester disease (figure 3), ALK-positive histiocytosis (4), HLH (5), Rosai-Dorfmann (6) and juvenile xanthogranulomatous histiocytosis (7).   Conclusion: The radiologist’s role in accurate recognition of these features and understanding the implications are integral for prognostication and optimal patient outcome.

1. Emile JF, Abla O, Fraitag S et al. Revised classification of histiocytoses and neoplasms of the of the macrophage-dendritic cell lineages. Blood 2016; 127(22): 2672-2681 2. Prayer D, Grois N, Prosch H et al. MR imaging presentation of intracranial disease associated with Langerhans cell histiocytosis. Am J Neuroradiol 2004; 25(5): 880-891