Gorham-Stout disease is a rare entity characterized by spontaneous progressive resorption of bone matrix, which is replaced by proliferative vascular and lymphatic canals and subsequently replaced by fibrous tissue.
The tibial and fibular involvement as presented in our case is an uncommon location for GSD. Meanwhile, this case also represents one of the few GSD involving the joints (less than 5 cases had been described in the literature, but malleolus was not referred). The pathogenesis of this disease has not been fully elucidated. Although some studies have described several patients with a history of preceding trauma like our cases, the association of this disease with antecedent trauma has not been clarified [5, 9]. The hypothesis is that GSD might be triggered by a trauma, resulting in an imbalance between the activities of osteoblasts and osteoclasts to induce the isolated but progressive bone resorption [17,18,19].
Since GSD is a diagnosis by exclusion, the final diagnosis is established based on clinical features, radiological and histological findings. To reach a proper diagnosis clinician need to exclude other differential diagnosis, such as potentially infectious, inflammatory, metabolic or endocrine disease and malignant tumors. Additionally, GSD must also be distinguished from other idiopathic osteolysis classification because it is nonhereditary without concomitant nephropathy . Hyperparathyroidism is the common endocrine disorders with potential complications on the musculoskeletal system, eventually leading to pathological fractures. Therefore, PTH level, calcium and phosphorus values should be included in laboratory tests for differential diagnostics of GSD. Some neoplastic processes which can cause the osteolysis should also be noticed, such as angiomas, aneurysmal bone cyst, eosinophilic granuloma in children.
In the radiographs, four distinct stages of GSD can be recognized . The first stage shows patchy osteopenia in the intramedullary or subcortical regions resembling osteoporosis. At the second stage, progressive osteopenia and cortical erosion without sclerosis. The third stage is characterized by adjacent soft tissue involving. At the final stage, the affected bone is complete resorption and filled with fibrous tissue. The bone window setting and 3-dimensional CT images are useful to depict the extent of bone destruction. Although, MRI can distinctly depict the extent of lesion but is nonspecific. MRI shows hypointensity and hyperintensity on T1 and T2-weighted images, with heterogeneous peripheral gadolinium enhancement. These findings and soft-tissue involvement usually mislead to a diagnosis of malignant tumor, especially multiple sites and pelvic involvement, such as Ewing’s sarcoma, metastasis, osteosarcoma, and multiple myeloma. Bone scintigraphy and whole-body positron emission tomography (PET) imaging can reflect the bone metabolic activity of regional lesion which are extremely useful to rule out the neoplastic or infective pathology [22,23,24]. Recently, Fluorine-18-sodium fluoride (18F-NaF) PET/CT has been proposed as a more bone-specific agent than Fluorine-18-Fluoro-D-glucose (18F-FDG) PET/CT and may be a useful approach for GSD diagnosis as well as assessment of disease activity and treatment response .
The patient in this study was followed up 8 years without progression. But the clinical course of GSD is unpredictable. It varies from being self-limiting, with mild manifestations, to a fatal outcome . Despite GSD is a benign disease, it can cause fatal outcomes when the crucial anatomical location was affected, such as cervical spine, mediastinum, ribs.
There are no definitive therapy recommendations for GSD. Medical therapy including bisphosphonate, vitamin D, interferon-alpha-2b, calcium, the anti-VEGF-A antibody bevacizumab, low molecular weight heparin, steroids can stabilize the bone destruction and halt the progression of the disease [26,27,28,29,30]. According to the literature, bisphosphonate has been shown to be more effective in the treatment of GSD compared with other regimens [26, 31, 32]. It increases the apoptosis of osteoclasts, diminishes the osteoclast precursor cells amount and reduces the activity of osteoclasts with no action on bone formation. However, there is no consensus about adequate doses, frequency and duration. Monthly i.v. injection is mostly preferred but the duration of treatment differs in the literature [9, 32,33,34].
Although radiotherapy has been reported to be successful in some radiosensitive cases, the results are controversial and there is no optimal radiotherapy dose for GSD [35, 36]. German Cooperative Group on Radiotherapy for Benign Diseases concluded that radiation therapy can effectively prevent progression of GSD in 80% of case, and advocated dose range of 30 to 45 Gy at 1.8 Gy to 2 Gy per fraction . Of note, radiation could provoke serious side effects, like secondary malignancy and growth restriction in children and adolescents who received high-dose therapy [11, 38].
Surgical treatments are recommended for pathological fractures or reconstruction of massively destroyed bones. Surgery for this disease includes resection alone, resection with endo-prosthetic reconstruction, and resection with biological reconstruction (autogenous bone grafting or allogenous bone graft). Resection alone may be suitable for some dispensable anatomical architectures, such as iliac bone, clavicle, proximal fibula, scapula. While for weight-bearing bone, such as femur, tibia, humerus, reconstruction is mandatory. In our case, the lateral malleolus (distal fibula and partial lateral distal tibia cortex) was involved, talus and medial malleolus were intact, but stability and range of motion of right malleolus were impaired. MRI shows the lesions with an obscure border and regional soft tissue edema which are not suitable for resection. The prior bisphosphonate treatment was applied to control the progression of lesion and regional edema. After 7 months of medical treatment, reossificiation makes the extent of lesion become distinct, therefore resection surgical treatment can be considered. We decided to perform the ankle arthrodesis with autologous fibular bone grafting matching the resected bone.
Ellati R et al. conducted a literature review including 64 cases of GSD and there were 29 cases that received surgical treatment. The follow up results showed that reconstruction with prosthesis cases were effectively controlled without recurrence, but all reconstruction with bone graft cases were progressive . Consistent with results from previous reports, reconstruction with bone graft increase the risk of recurrent bony resorption and shows a low success rate in controlling the progression of the disease [5, 39]. However, an eight-year follow up of our patient, the disease was controlled, and no recurrent resorption of bone was noted. We suppose the probable reason for routine biological reconstruction failure is a high risk of residual lesion during operation, and it easily causes recurrent osteolysis. It is important that the timing of resection with reconstruction should depend on the degree of controlling this disease. The reoccurrence of ossifications and bone regrowth indicate the arrest of osteolysis, and thereafter a surgical therapy for GSD can be considered. Ossifications and sclerosis make the extent of lesion distinct that simplifies the intraoperative manipulation, prevent unintended burst of the tumor and avoid lesion residual. Meanwhile, regression of soft tissue swelling can help to reduce the incidence of wound complication. With regard to some special anatomical location (such as malleolus, radiocarpal joint, shaft of radius and ulna), biological reconstruction will be more suitable than endo-prosthetic reconstruction.
In conclusion, although the previous studies demonstrated that biological reconstruction alone is not effective to control the disease, combining medication with biological reconstruction may constitute an effective approach of treatment. This novel combination was not previously reported in literature for the treatment of GSD, and show a result of well-controlling the disease and no progression at eight-year follow up.