Pediatric Langerhans Cell Histiocytosis: Unifocal Localization in the Frontal Bone Presenting With Periorbital Swelling

<b>Background:</b> Langerhans cell histiocytosis is a rare disease, the pathogenesis of which remains a subject of debate, with considerations of either a neoplastic origin or an inflammatory nature. It arises from the uncontrolled proliferation of immature myeloid dendritic cells, leading to their accumulation in various sites. Recent studies indicate that Langerhans cell histiocytosis is a clonal neoplastic disorder driven by mutations in the MAP kinase pathway. When the bones are involved, the condition is often asymptomatic, but it can cause pain or soft tissue swelling, with the skull being the most affected site. <b>Case Presentation:</b> We present the case of a 9-year-old boy who presented with painful left periorbital swelling. He initially underwent empirical medical therapy for suspected periorbital cellulitis. Due to a lack of improvement in symptoms, radiological assessment was subsequently performed, revealing frontoethmoidal-orbital bone resorption and a mass of ambiguous nature with peripheral enhancement in T1-weighted sequences. Following an ENT evaluation, a biopsy was performed using an endoscopic endonasal approach. The histological examination confirmed the presence of Langerhans cell histiocytosis, with unifocal localization in the frontal bone. Consequently, the patient began chemotherapy following the LCH-IV protocol, the international collaborative treatment protocol for children and adolescents with Langerhans cell histiocytosis. <b>Conclusions:</b> Langerhans cell histiocytosis is a rare disease that may present with involvement of the frontal and ocular regions. Although periorbital cellulitis is initially treated with first-line medical therapy, if there is no improvement, radiological assessment and subsequent histological examination become essential for prompt diagnosis and appropriate therapeutic intervention.