OF and FD are diseases that often require differential diagnosis because of overlaps and similarities in their clinical, radiological, and morphological characteristics.28 This poses a dilemma for pathologists, especially in the absence of typical features and the frequent existence of histological alterations.29 Although previous research by our research group showed that the GNAS gene is a reliable adjunct for differentiating between OF and FD of the jaw,30 GNAS mutations can only be detected in 45%–88% of FD cases, leaving a challenging situation for undetected lesions. The gene discussed is GNAS; the disease is Fabry disease.