Primary hydatid disease of the humerus.

Introduction Hydatid disease is a parasitic tapeworm infection caused by Echinococcus species. E.granulosus and E.alveolaris are the most common causes of hydatid disease in humans. Hydatidosis is endemic in the sheep-raising districts of Australia, South America, Central Asia, the Middle East and the Mediterranean countries. Osseous involvement is rare and bone lesions are reported in only 0.5% to 4.0% of the cases. Isolated primary hydatid disease of the bone without hepatic or pulmonary involvement is extremely rare, as the the parasite has to cross pulmonary and hepatic barriers before reaching the bone.1 Moreover, the humerus is an unexpected site for osseous involvement.2-4 Due to its rarity, it often presents a clinical and radiological diagnostic challenge. Treatment of osseous lesions is also difficult because of the invasive nature of bony involvement and the spillage of fluid with subsequent seeding.1,5