Mazabraud’s Syndrome is a rare benign disorder characterised by the association of two hallmark entities: fibrous dysplasia (FD) and intramuscular myxomas (IM). The aetiology of the disease is unclear, but molecular research of FD and IM points in the direction of post-zygotic mutations in the guanine nucleotide binding protein, alpha stimulating (GNAS) gene, which activates a trophic cascade leading to aberrant cellular proliferation. Although the diagnosis of Mazabraud’s Syndrome is rare, showing a prevalence lower than 1/1,000,000, it should be suspected in every patient presenting with FD and IM. These patients should get a bone scintigraphy and a magnetic resonance imaging (MRI) of the affected anatomical area. Other imaging techniques, such as positron emission tomography-computed tomography (PET-CT), may have additional value. Finally, the patients should perform a biopsy of the IM to confirm the diagnosis. The treatment includes bisphosphonates for FD, and surgery is reserved only for severe cases with persistent pain, deformity, fracture, or risk for a pathological fracture. Asymptomatic IM should be treated conservatively, but symptomatic lesions can be surgically excised. Follow-up is useful since malignant transformation of FD and recurrence of IM after excision are reported in the literature.

(BELG J MED ONCOL 2022;16(4):187–90)