Mazabraud syndrome

A 57-year-old man was initially referred to gastroenterology following stomach pain and change in bowel habits. CT chest abdomen pelvis was performed which demonstrated a lesion in the right proximal femur. The patient was asymptomatic, with normal lower limb examination. Recent blood tests were normal with normal bone profile and CRP.

CT chest abdomen pelvis (Fig 1) depicted a sclerotic intramedullary abnormality within the right proximal femur. Plain radiograph (Fig 2) demonstrated the sharply marginated sclerotic intramedullary abnormality with slight bone expansion. There was intramedullary lucency in the mid femoral shaft with some ground glass appearance within the mid–diaphysis. This prompted MRI (Fig 3) of the femur which showed the proximal femoral lesion to return a very low T1 and T2 weighted signal. There was elongated low T1 and bright signal on the T1 TIRM sequences with interspersed normal marrow fat within the entire femoral shaft. Another lesion was seen in the intramuscular location within the vastus lateralis returning a T1 isointense and fluid bright signal intensity on the fluid-sensitive sequences. Ultrasound (Fig 4) of the soft tissue lesion demonstrated a very well-defined ovoid hypoechoic soft tissue lesion with no internal vascularity.

Fibrous dysplasia is a congenital disorder resulting from sporadic mutation in the GNAS gene characterised by replacement of normal marrow with poorly organised and immature fibrous tissue. The fibrous tissue can undergo varying degrees of ossification producing the typical ground glass matrix on the pain radiograph. It can be localised to a single bone (monostotic FD) or involve multiple bones (polyostotic ). Mazabraud syndrome is a rare association between FD and intramuscular myxomas. To date, there are less than 100 cases reported in literature. It is mostly seen in association with the polyostotic FD. Typically, the intramuscular lesion occurs in the vicinity of the bony abnormality and tend to involve same anatomical region. Thigh is the most common site of intramuscular myxoma in Mazabraud syndrome with associated fibrous dysplasia involving the ipsilateral femur. Fibrous dysplasia can be asymptomatic or present with skeletal deformity, pain and fractures. The MRI signal characteristic depends on the relative proportion of the fibrous tissue, trabecular bone, cystic and haemorrhagic components. The myxomas are well-defined and well-circumscribed intramuscular lesions having a very bright signal on the fluid-sensitive sequences. It is iso – hypointense to the surrounding musculature on the T1 weighted images. Though they return a very bright signal on the fluid-sensitive sequences, sometimes resembling cysts or ganglions, they are solid tumours with variable vascularity and demonstrate heterogeneous enhancement on contrast administration. Myxomas are benign, but a histopathological diagnosis is a must to exclude malignancy or metastasis. The myxomas in Mazabraud syndrome have not been reported to have a malignant transformation, though there is an increased risk of sarcomatous transformation of the fibrous dysplasia. As a result, it is important for a radiologist to identify this syndrome, confirm the diagnosis by tissue sampling and recommend clinical follow-up.