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and maxillofacial pathology diagnosis and management—from page 117
Langerhans Cell Histiocytosis Discussion Langerhans cell histiocytosis (LCH) was previously known as “histiocytosis X”, because of a poor understanding of its etiology.1,2 It is now known to be a reticuloendothelial system disorder manifesting as a clonal disease of myeloid dendritic cells.3 Although LCH has been diagnosed in all age groups, the disease predominantly affects children in the age range of 1 to 4 years.3 The relative rarity of LCH increases the risk of underdiagnosis and misdiagnosis, and therefore underscores the need for a high index of suspicion for osteolytic bone lesions presenting with no apparent etiology.4 Historically, LCH was characterized by 3 clinical variants: Letterer-Siwe, affecting mainly infants, presents as an acute disseminated disease involving multiple organ systems; Hand-SchullerChristian disease, which
also may involve the skeletal and extraskeletal tissues; and eosinophilic granuloma, which presents as a chronic, localized form of LCH typically involving the skeleton, but occasionally also extraskeletal tissues in adults.4 A congenital and syndromic form of LCH, called Hashimoto– Pritzker syndrome, is also recognized, and patients present with deep subcutaneous skin lesions.4 A recent revision of the classification of histiocytosis by the Histiocyte Society, classifies LCH as “single system”-, “lung”- and “multisystem” based on site and organ (liver, spleen, bone marrow) dysfunction.4,5 In single system LCH, the skin is most commonly affected, followed by the lymph nodes and lungs.6 When the skeleton is affected, the skull, long bones, pelvis, ribs, vertebra, and posterior mandible are the most common sites.4,7
Clinical presentations of oral cavity LCH are hardly straight forward resulting in significant challenges when attempting to establish a differential diagnosis. Common sites are the jaw bones as well as the gingiva and periodontium. In these locations, the clinical features often mimic a constellation of more common entities related to periodontal diseases, such as gingival epulides, granulomatous or ulcerative lesions, or malignancies.8,9 Furthermore, early intraoral lesions confined to the maxillofacial skeleton are not always apparent during oral examination and are only discovered fortuitously on radiographs, where they present as radiolucent osteolytic processes. Such instances generate additional considerations in the differential diagnosis, including odontogenic lesions, as in the present case, thereby necessitating a biopsy to determine the histopathologic diagnosis of the lesion. Radiographically, LCH of the jaw presents as www.tda.org | March 2022
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