Mutation of the GS gene occurs early indevelopment, and results in a mosaic of abnormal and mutated cells. The manifestations of MAS in each individual depend upon the extent and distribution of abnormal cells. Abnormal and prolonged activation of multiple peripheral endocrine glands occurs even while the necessary stimulatory pituitary hormones may be absent. Precocious puberty, with onset of breast development, pubic hair, and the onset of menses as early as the first few months of life may occur in females. Other manifestations include acromegaly, hyperthyroidism, hyperprolactinemia, and others.
Treatment depends on the manifestations and extent of the disease. Bone fracture lead to the need for orthopedic stabilization and joint replacement due to periarticular fracures.
The general overall prognosis for patients with this syndrome is good, but the extent of involvement may lead to severe dysfunction of affected organs, including the hepatobiliary system, cardiopulmonary system, and virtually any affected organ, leading to risk factors for early death.
The pathological findings in the involved bones include classic features of fibrous dysplasia. On microscopic analysis, there is fibrous connective tissue containing immature trabeculae of a woven, non-lamellar bone. These immature trabeculae may have a characteristic "Chinese letter" or "alphabet soup" appearance, resembling partially formed letters or symbols.
On radiographs, the affected bones have multiple, expansile, mostly lucent lesions which contained a fine matrix described as " ground glass." The normal trabecular pattern is absent. The tumors are a radiolucent area with a sclerotic rim, and may slightly expand or thin the nearby bone cortex. The matrix of the lesion has a "milky" or "ground glass" appearance due to the very fine bony trabeculae contained within the tumor.
Frequently involved bones include the femur, the tibia, the facial skeleton, and the ribs. Bone fragility and associated fractures are common, and weight-bearing bones may suffer multiple fractures. In the proximal femurs, multiple successive cortical microfractures may result in characteristic bowing of the proximal end of the bone into a "shepherd's crook" deformity.
On bone scan, fibrous dysplasia lesions typically demonstrate
increased uptake. However, 10% to 15% of lesions do not have increased radiotracer uptake and appear "cold" on bone scans.
Pamidronate treatment of patient's with polyostotic fibrous dysplasia has shown encouraging results. Pamidronate seems to reduce the fracture rate and reduce the bone pain associated with the lesions. The benefit of pamidronate in polyostotic fibrous dysplasia has been conclusively demonstrated. Bone pain, fracture risks, bone density, and metabolic indices of bone turnover show favorable response to treatment. However, some authors have reported that in developing children, dysplastic lesions in long bones continued to undergo expansion despite pamidronate treatment.
For developing children, the authors of this website recommend early and aggressive intervention with pamidronate, frequent follow-up, and orthopedic stabilization of at-risk long bones, using appropriate expandable or non-expandable intramedullary devices. The femoral neck and proximal femur are at particularly high risk, and early prophylactic intramedullary rodding with a cephalomedullary device is recommended, before the microfractures and deformity begin to develop.
Clinical signs of sarcomatous degeneration include pain and swelling at the site of the lesion. The most reliable radiographic sign is extension of the lesion through the cortex into the surrounding soft tissues. Since osteosarcoma is the most common histologic type of sarcoma that may occur, bone formation within the soft tissue mass would be a particularly worrisome sign.
Presentation of a case of MAS
The patient is a very pleasant 35-year-old woman who works as a cashier. She has pain in the top of the right proximal femur. The pain is exacerbated by walking and prolonged standing. It is relieved by rest.
The patient has a history of a syndrome affecting both her endocrine system and skeletal development. She has short stature. She is now 4-foot 3 inches in height.
The patient had a previous fracture of the left proximal femur which eventually required hip replacement. She gets infusions of pamidronate once every two months.
On examination the patient has short stature as noted above. Her right hip is carried higher than the left. The right hip has excellent full free range of motion. Pressure on the right trochanter and the right femur causes pain. There is a large café au lait spot over the right side of the neck and over the back. It has a regular border.
The patient has x-rays made. There are multiple lesions in multiple bones. There are multiple lesions in the right femur. Distal to about the junction of the middle and distal third of the femur, the bone is more normal.
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What is the diagnosis?
1 comment:
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