Hydatid disease of proximal femur treated using a mega prosthesis: A case report

•Bone Hydatidosis has nonspecific clinical and radiological signs.•These characters may lead to late or misdiagnosis situation.•Anamnesis is very important, it could guide the diagnosis.•The diffuse and infiltrative characters of bone hydatidosis make it challenging to manage.•The reconstruction prosthesis allows extensive resection without damaging the function. Bone hydatidosis is a rare disease. It is characterised by discreet and nonspecific symptomatology that makes the diagnosis late and the treatment difficult to manage. We report the case of a 29-year-old woman hospitalised for right hip pain with a lytic image well limited in the upper extremity of the right femur. We retained the diagnosis of a unicameral bone cyst which weakens the cortical bone. Osteosynthesis with a Gamma nailing was indicated to prevent fractures. At five years of follow up, the patient presented a pain recurrence. Radiographs showed almost a destruction of the upper extremity of the femur and a loosening of osteosynthesis material. Thus, we indicated the removal of the osteosynthesis material and a bone biopsy were performed. Histopathological examination leads to an osseous hydatid cyst diagnosis. We decide to carry out a carcinological resection and reconstruction with a mega prosthesis. The clinical results were excellent and no recurrence for three years follow-up. Bone hydatidosis is challenging to diagnose at an early stage, mainly when it simulates a bone cyst. Moreover, the consequence of a late or misdiagnosed bone hydatidosis is devastating. Because of its diffuse and infiltrative character, it gradually invades the whole bone, which makes it more complicated to manage. Bone hydatidosis is a rare disease that can simulate other pathologies like a bone cyst in our case. In these situations, the anamnesis has a primordial place to guide the diagnosis and investigations.