Multimodality imaging features of orbital Necrobiotic Xantogranuloma (XNG)

Abstract

Background Necrobiotic xanthogranuloma (NXG) is a rare non-Langerhans histiocytosis that primarily manifests as skin lesions and is often associated with hematologic disorders, particularly monoclonal gammopathy. The orbit is the most common site of extracutaneous involvement in NXG. Since its first description in 1980, the molecular pathology and dermatologic characteristics of NXG have been extensively studied. However, there is no comprehensive multimodality description of the imaging features of orbital NXG in the literature. This study aimed to describe the imaging features of NXG and provide a brief overview of the imaging differentials. Patient presentation : A 16-year-old young man with an underlying immunologic imbalance was referred to our center for evaluation of a 9-year history of a slowly growing right orbital mass, which resulted in vision loss in his right eye. His medical history included systemic juvenile rheumatoid arthritis (sJRA) and a genetic abnormality that predisposed him to immunologic imbalance. To further characterize the orbital lesion, CT, MRI, and FDG PET/MRI were performed. A biopsy of the most hypermetabolic component of the infiltrative retro-orbital mass confirmed the diagnosis of NXG. He underwent high-dose IVIG therapy and bone marrow stem cell transplantation, which resulted in a slight reduction in the right orbital mass. Conclusion This paper presents the first multimodality imaging features of orbital necrobiotic xanthogranuloma in an adolescent patient.