ABSTRACT
Hydatidosis is an endemic disease in different parts of the world. Its causal agent is the cestode from the genus Echinococcus. The most commonly affected organs in humans are liver and lung. Bone hydatid disease is a very rare entity, accounting for 0.5 to 4% of total cases. We report a case of a 58 year-old woman from La Rioja, Argentina, who consulted for left infapatellar pain and walking disability of eight months duration. Imaging studies showed a cystic lesion which involved metaphysis and diaphysis of left proximal tibia. Surgical resection was performed and histopathological study confirmed that it was a hydatid cyst. The patient did well and completed three cycles of treatment with albendazole. Currently, she has no evidence of disease and she recovered motility of her left leg. Primary hydatid bone disease, where there is no evidence of systemic disease, is even more unusual. Tibia involvement occurs in up to 15% of the cases. These lesions clinically manifest when they suffer any type of complications. Preoperative diagnosis is mainly made by imaging studies. Lesions are usually osteolytic and can involve cortical bone and extend to soft tissues. Differential diagnosis with inflammatory processes and bone tumors should is mandatory. Treatment is surgical and prognosis is poor due to its high morbi-mortality rate and recurrence risk from 70 to 80%.