Biological Behavior of Craniofacial Fibrous Dysplasia in McCune-Albright Syndrome Compared With Nonsyndromic Disease

BACKGROUND: Fibrous dysplasia (FD) is a postzygotic mosaic disorder caused by activating GNAS mutations, resulting in the replacement of normal bone with fibro-osseous tissue. FD is classified as monostotic (MFD), polyostotic (PFD), or McCune-Albright syndrome (MAS), and skeletal lesions may demonstrate either aggressive or nonaggressive biological behavior. The purpose of this study was to evaluate whether FD subtype was associated with the biological behavior of craniofacial skeletal lesions. METHODS: This was a retrospective cohort study of subjects with craniofacial FD/MAS treated at Boston Children's Hospital from 1998 to 2025. The predictor variable was FD subtype, and the primary outcome was biological behavior. Categorical variables were analyzed using χ 2 and Fisher tests. Continuous variables were assessed with ANOVA. Pairwise comparisons were performed for significant findings. Significance was defined as P <0.05. RESULTS: Fifty-seven subjects were included, with a mean age of 10.4±4.7 years. Aggressive biological behavior was observed in 5 (62.5%) subjects with MAS, 15 (42.9%) with PFD, and 3 (21.4%) with MFD ( P =0.15). Craniofacial swelling was the most common presenting symptom in MFD (50.0%) and PFD (40.0%), and precocious puberty was the most common in MAS (62.5%). MAS was associated with higher rates of pelvic, spine, and rib involvement than PFD ( P <0.05). It also had greater rates of skull base, optic canal, and nasal involvement than MFD ( P <0.05). CONCLUSIONS: McCune-Albright syndrome demonstrated a high rate of aggressive craniofacial FD behavior, though not significantly greater than MFD or PFD. MAS demonstrated the most extensive craniofacial and noncraniofacial skeletal involvement.