Background: Langerhans' cell histiocytosis (LCH) is a group of conditions affecting the reticuloendothelial system. It includes Letterer-Siwe disease, Hand-Schuller-Christian disease and eosinophilic granuloma and most often presents in childhood. Materials and methods: Twenty-five cases of LCH were diagnosed histologically and confirmed by CD1a antibody and assessed immunohistochemically using anti-RANKL and anti-RANK antibodies to evaluate osteoclastogenic mechanism. Results: Regarding jaw cases, there was a significant correlation between CD1a and RANK (P=0.016). While in the skull, highly significant correlation existed between RANK and RANKL (p=0.001). Among the sites, there was no statistically significant difference found for each the immunohistochemical markers used. Conclusion: LCH of jaws and skull bear similar osteoclastogenic mechanism when quantified with RANK and RANKL immunostaining respectively. With a significant correlation between CD1a and RANK for jaw cases, while in the skull lesions, there was a high significant correlation between RANK and RANKL. Keywords: Langerhans cell histiocytosis (LCH), receptor activator of nuclear factor kappa-B ligand(RANKL), receptor activator of nuclear factor kappa-B (RANK),cluster of differentiation(CD1a), Langerhans cells(LCs).
