A 76 year old lady was referred with increasing paraspinal and left buttock pain over the past year. She had a previous liposarcoma excised from her left gluteal region 25 years ago. There was no history of systemic upset or recent weight loss. On examination, no masses were palpable.
MRI was subsequently performed for further evaluation. This shows multiple osseous lesions associated with well-defined soft tissue masses with the largest one in the left gluteal region. The osseous lesions are heterogeneously intermediate on T1W( figure 1a) and heterogeneously high on STIR (figure 1b), consistent with fibrous dysplasia . The soft tissue masses are homogeneous with low signal on T1W(figure 2a) and high intensity on STIR images (figure 2b). The post-contrast images demonstrate heterogeneous central enhancement (figure 3b) when compared to the non contrast T1W (figure 3a). Given the previous history of liposarcoma a biopsy was performed to exclude disease recurrence and the histology result confirmed that the lesions are myxomas.
Mazabrauds syndrome is a rare syndrome first described in 1967, characterised by the association of fibrous dysplasia, which can involve one bone (monostotic) or greater than one (polyostotic), and single or multiple benign intramuscular myxomas[1] . The aetiology of the syndrome is unknown, it has been proposed that the somatic mutations in the GNAS1 gene play a role[2, 3]. The gene has also been described in disorders such as McCune-Albright syndrome (triad of polyostotic fibrous dysplasia, café-au-lait spots and precocious puberty)[4, 5] and fibrous dysplasia. The intramuscular soft tissue myxomas component of Mazabrauds syndrome typically presents in the 6th decade and follow a benign course. These lesions are considered to be soft tissue hamartomas with tumour like growth[1, 6].
The lower limbs are classically affected, most commonly the right[4]. Patients often present with long standing painless soft tissue masses, a history of bone pain or recurrent fractures secondary to the bone dysplasia[7]. The associated soft tissue myxomas are located in close vicinity to the osseous component[1]. The syndrome more commonly affects females [6, 8].
Fibrous dysplasia is a congenital process, where there is a localised defect in osteoblastic differentiation and maturation. The normal bone is replaced with fibrous stoma and islands of immature bone which predominantly develop in children and young adults. Fibrous dysplasia has a reported 1-8% risk of malignant transformation into osteosarcoma[7, 9].
Typically, radiographic appearances of myxomas show a non-specific soft tissue mass. On MRI, the masses are well-defined and homogenous with low signal on T1 and high signal on T2 weighted images as in our case. The post contrast images usually show heterogeneous central enhancement and also rim enhancement of the pseudo capsule [10]. In our case there was heterogeneous central enhancement but no convincing enhancement of the pseudocaspule. The soft tissue masses are closely associated with hyperintense osseous lesions on T2 weighted images, which are the regions of fibrous dysplasia.
Mazabrauds syndrome is generally managed conservatively, however in some cases the myxomas can be resected if they are causing symptoms but there is a high risk of recurrence [5, 10].
In conclusion Mazzabarauds syndrome should be considered early in patients presenting with fibrous dysplasia and soft tissue masses, especially if the soft tissue lesion is myxoid in nature, as it is generally managed conservatively.
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Mazzabarauds syndrome
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Based on the provided pelvic/hip MRI sequence images, the following main features can be observed:
• A localized abnormal signal is visible in the left iliac bone and surrounding soft tissues. Fibrous structural changes are observed within the bone, appearing as isointense or hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences, suggesting fibrous proliferation or fibrous bone lesions.
• In the iliacus, gluteal muscles, or adjacent soft tissues, a well-defined, round or ovoid soft tissue lesion is seen. It is hyperintense on T2-weighted sequences and mainly hypointense or slightly hypointense on T1-weighted sequences. After contrast enhancement, central or heterogeneous enhancement is visible, consistent with a myxoid lesion (e.g., intramuscular myxoma).
• Overall, no significant extensive invasive or destructive changes in the bone are apparent, nor is there any notable large soft tissue mass invading surrounding bones or joint surfaces.
• There is no clear sign of recurrent liposarcoma in the previously operated area of the left buttock. At least on imaging, no suspicious lesion consistent with that pathology is detected.
Taking into account the patient’s advanced age of 76, the absence of significant systemic symptoms, and the imaging findings showing a myxoid soft tissue lesion closely adjacent to fibrous bone changes—with a relatively benign appearance and no obvious invasive signs—the most likely diagnosis is:
Mazabraud syndrome (fibrous bone lesions combined with intramuscular myxoma).
If there is further clinical doubt or need to exclude tumor recurrence, a biopsy or pathological examination can be performed to clarify the nature of the soft tissue lesion.
Treatment Strategy:
1) Conservative Observation: For patients suggestive of Mazabraud syndrome, if clinical symptoms are mild and the lesion is stable or slowly progressing, regular follow-up and conservative management can be adopted. This includes monitoring lesion size, periodic MRI checks, and pain control.
2) Surgical Intervention: For large lesions or those causing significant symptoms (pain, local pressure, etc.), surgical resection of the intramuscular myxoma may be considered to alleviate symptoms. However, myxomas carry some risk of recurrence, so the overall condition of the patient should be carefully evaluated.
3) Other Treatments: If a fibrous bone lesion shows pathological fractures or severe pain, surgical stabilization or medical therapies (e.g., bisphosphonates to reduce bone pain) may be considered. Additionally, attention should be paid to osteoporosis and muscle atrophy; supplementation with calcium and vitamin D, along with anti-osteoporosis treatment, may be necessary.
Rehabilitation/Exercise Prescription:
• Gradual Progression and Individualization: Owing to the patient’s advanced age and existing bone abnormalities, safe, low-impact exercises should be selected under the guidance of a specialist or physical therapist.
• Exercise Method: Begin with lower-limb strength training and range-of-motion exercises in seated or semi-reclined positions, such as leg lifts, ankle dorsiflexion, and plantarflexion. Progress gradually to sitting-to-standing transitions, short-distance walking, and simple weight-bearing exercises with support.
• FITT-VP Principle:
– Frequency: 3–5 times per week, gradually increasing according to tolerance.
– Intensity: Begin with low intensity (e.g., RPE 3–4), ensuring it does not exacerbate pain or lead to excessive fatigue.
– Time: 10–20 minutes per session initially, with duration extended progressively as tolerated.
– Type: Prefer exercises with high safety and controllability, such as elliptical machines, stationary bikes, or aquatic exercises.
– Progression: Once adapted, introduce light resistance training, monitoring the hip and lumbar spine for safety and to prevent fractures.
– Volume: Combine subjective patient feedback with objective measures (heart rate, pain level, etc.) to plan the total weekly exercise volume.
• Precautions: Prevent falls and avoid excessive weight-bearing and high-impact activities. If severe pain, joint swelling, or other abnormalities occur, seek medical advice promptly.
This report is based solely on the provided medical history and imaging for reference and does not replace an in-person clinical evaluation or the professional opinion of a physician. If the patient has any questions or experiences any changes in symptoms, they should be advised to seek further evaluation and consultation at a hospital promptly.
Mazzabarauds syndrome
