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.
Mazabraud syndrome
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Based on the provided CT and X-ray images, there is a bone lesion in the proximal right femur showing a “ground-glass-like” density change with relatively clear margins. Fibrous or partially calcified/ossified appearances can be seen inside, consistent with the typical imaging features of a fibrous lesion. MRI sequences reveal a well-defined soft tissue lesion in the thigh muscle layer (especially in the quadriceps or adductor region), appearing isointense or slightly hypointense on T1-weighted images, hyperintense on T2-weighted and fat-suppressed sequences, with a certain degree of heterogeneous enhancement after contrast administration, suggesting a possible soft tissue myxoma lesion. Ultrasound images also show a regularly shaped, well-defined elliptical hypoechoic area.
The above bone lesion corresponds to the adjacent soft tissue lesion, and the patient currently shows no significant pain or functional impairment in the lower limb upon physical examination. Serological tests (e.g., bone metabolism markers, inflammatory markers) reveal no notable abnormalities.
“Ground-glass-like” density changes in bone are a common feature of FD, which often occurs in adolescents and young adults but can be seen at any age. It can present in a monostotic or polyostotic form.
This refers to the coexistence of FD and intramuscular myxoma; it is relatively rare, but the combination of a fibrous bone lesion and a high-signal soft tissue mass in the thigh strongly suggests their correlation.
Although the patient’s blood tests are normal, malignant tumors should still be considered in incidental bone lesions. However, given the “ground-glass-like” appearance on imaging and the painless, solitary nature of the lesion, malignancy is relatively less likely.
Taking into account the patient’s age, lack of prominent clinical symptoms, the typical “ground-glass” bone lesion on imaging, and the presence of an intramuscular myxoma-like lesion, the most likely diagnosis is Mazabraud Syndrome (Fibrous Dysplasia coexisting with Intramuscular Myxoma). A biopsy is still required to exclude malignancy or other pathologies before definitive confirmation.
Since the patient currently experiences no significant pain or functional impairment in the lower limb and the overall bone strength appears adequate, rehabilitation should be gradual and individualized. Emphasis should be placed on protecting the lesion site, avoiding excessive weight-bearing or impact.
Throughout the rehabilitation process, regular medical follow-up and imaging re-evaluation are essential to rule out lesion progression or complications.
Disclaimer: This medical imaging analysis report is based solely on the provided information for reference purposes. It does not replace in-person consultation or guidance by a professional physician. Final diagnosis and treatment plans should integrate complete clinical data, pathological results, and professional medical evaluation.
Mazabraud syndrome
