Preliminary anteroposterior (Figure 1A) and lateral (Figure 1B) radiograph examinations of the right hip joint indicated that the femoral head had disappeared and that the margins of the femoral neck and acetabulum were incomplete, which were further confirmed by 3D reconstruction images (Figure 1C) and CT scan images (Figures 1D,E). In particular, the 3D reconstruction and CT scan images clearly demonstrated the range of local osteolysis involving the acetabulum and femoral neck. MRI images (Figures 1F-I) showed hypointensity on T1-weighted images, extensive hyperintensity on fat-suppressed T2-weighted images, and massive joint effusion in the right hip joint. To further clarify the progression of the disease, ECT examination (Figure 2) was performed and the results showed increased focal concentrations of radiotracers in the right femoral head, femoral neck, and acetabulum. Therefore, we highly suspected that this patient may be diagnosed with a malignant bone tumor with aggressive osteolytic lesions. In addition, the chest radiograph was normal, and no obvious signs of tuberculosis were found. Laboratory blood tests showed normal levels of leukocytes, neutrophil granulocyte ratio, hypersensitive C-reactive protein, erythrocyte sedimentation rate, serum calcium, phosphorous, alkaline phosphatase, and parathyroid hormone. Oncology indicators such as alpha fetoprotein, carcinoembryonic antigen and PSA were all within the normal range. The T-SPOT test was negative. To further clarify the diagnosis, an open biopsy of the right hip joint was performed under general anesthesia. A total of 6 cm3 tissues were obtained from the right femoral neck, synovial membrane, and acetabulum. Subsequent histological examinations showed that the necrotic bone tissue was accompanied by focal aggregation of osteoclasts, giant cells and plasma cells without cellular atypia, some proliferative thin-walled capillaries and lymphatic structures, and replaced by fibrous connective tissue (Figure 3). Combined with clinical manifestations, laboratory blood tests, radiological features and histopathology examinations, the patient met seven out of the eight diagnostic criteria for GSD proposed by Heffez et al. (Table 1). Eventually, the patient was diagnosed with GSD. The patient was then treated with medication, including bisphosphonates (4 mg/week, iv), vitamin D (600 UI/day), and calcium (600 mg/day) for one month. The surgical criteria for total hip replacement in patients with GSD were considered as follows: (i) the patient was 70 years old; (ii) The GSD lesions had involved the acetabulum and the neck of the femur, and in a serious case, the femoral head had completely disappeared. (iii) Contraindications to surgery have been ruled out by relevant examinations. (iii) The patient has a strong need to restore lower limb motor function. We first completely removed the GSD-accumulated bone with the assistance of intraoperative pathologic examination, and then fitted a total hip arthroplasty rather than femoral head arthroplasty to account for the GSD lesions that had accumulated in the acetabulum. To restore the normal walking function of the lower limbs, we performed complete excision of the necrotic tissue followed by total hip arthroplasty. At the 3-year follow-up after surgery, the patient had no pain in the right hip when walking long distances or bearing weight. Radiographs showed that the hip prosthesis was in place and not loose. Moreover, no signs of recurrence were observed in the right hip joint (Figure 4).