Primary cystic echinococcosis presented as prolonged disabling knee osteoarthritis: a case report

Abstract

Cystic echinococcosis (hydatid disease) is a neglected tropical disease common in Asia, South America and Sub-Saharan Africa. It is a parasitic disease  caused by larval stage of Echinococcus granulosus. The commonest organs affected by hydatidosis are the liver and the lung. Primary bone hydatidosis  in humans is a rare disease accounting for 1–2% of echinococcosis cases. To our knowledge secondary hydatidosis of joints is uncommon and few cases of hydatid disease of the knee joint have been reported. We present a case of primary cystic echinococcosis of the knee joint occurring in a 43-year-old  female presenting mainly as disabling right knee arthritis in the form of chronic (13 years) painful swelling, which ultimately led to her inability to walk.  Imaging and histopathologic examination revealed cystic echinococcosis of the right knee joint. Subsequent pulmonary, liver and bone screening for  primary lesions were negative. To our knowledge, this is the first ever report on primary knee hydatid disease. It is possible that pre-existing arthritis  modulated the local environment of the knee, rendering it susceptible to hydatidosis. This should be taken into account in the differential diagnosis of  arthritis particularly in endemic areas.