Pelvic bone and hip joint hydatid disease revealing a retroperitoneal location.

Echinococcosis is a parasitic disease produced by the larval stage of Echinococcus granulosus. Hydatid disease of bone is rarely seen in humans and it has been reported in only 1-2% of cases of echinococcosis. We present a patient who developed hydatid disease of the left pelvic and femoral bones with cartilage destruction of the ipsilateral hip joint revealing a retroperitoneal location of hydatid cyst. Hydatid bone must be present in the differential diagnosis of chronic monoarthritis. Skeletal involvement is usually secondary to visceral hydatidosis that we must research. Early diagnosis allows eradication and salvage of the bone and the hip joint. Delayed diagnosis is always fraught with the risk of recurrence and sepsis.