Mazabraud syndrome is a rare condition known for association of intramuscular myxomas and fibrous dysplasia.

Until 2004 there were only 55 documented cases. The first desciptions were documented in 1926 by Henschen, and the syndrome features were first described in 1967 by Mazabraud.

The differential diagnosis is broad and includes:

• enchondroma
• chondrosarcoma
• bone cysts
• fibrous dysplasia
• osteosarcoma (especially in the form of monostotic fibrous dysplasia).

Myxoid lesions have to be distinguished mainly from malignant lesions like malignant histiocytoma, liposarcoma, sarcoma and chondrosarcoma. Patients often report painless mass which may be associated with bone deformities and fractures.

Molecular analysis revealed a mutation in the gene GNAS1. It is necessary to exclude malignancy histologically. Bone scintigraphy is suitable for determining the activity of the disease and multicentricity. CT is appropriate to determine the extent of bone lesions. Myxomas in MRI images are sharply defined (T1 hypointense, T2 hyperintese). After administration of contrast, you can differentiate the proportion of solid tissue and fibrous septa. Malignant transformation of myxoma is not recorded, although they are often present with local recurrence after incomplete resection. Treatment is mainly conservative, surgical solution is indicated for prevention of pathological fractures or bone deformities.