Hydatid disease of bone: a mimic of other skeletal pathologies.

Skeletal hydatidosis results from the deposition of the larval form of the Echinococcus, a genus of tapeworm. The incidence of bone disease is extremely low as most larvae are trapped by the liver and lung upon release of the embryo into the portal blood stream. The interpretation of imaging studies can prove very confusing because bone changes evolve with time, and the non-specificity of these findings often leads to a mistaken diagnosis. We present the case of a 35-year-old woman with long-standing pain in the left hip joint in which the findings on CT were thought of as being either tuberculous or neoplastic in nature. The result of a CT-guided biopsy and another done following surgery concurred on an unexpected diagnosis of a hydatid cyst. This case illustrates that in the absence of a high index of suspicion for echinococcal infection, the semblance of imaging findings of hydatid disease in bone to those of other skeletal pathologies can lead to misinterpretation.