Polyarthritis associated with hydatid disease (echinococcosis) of the liver.

A 36-year-old male developed asymmetric polyarthritis during the course of hydatid disease of the liver. Excision of the hydatid cyst was accompanied by full remission of the arthritis without recurrence during the 7-year follow-up period. This sequence of clinical events suggests an eventual cause and effect relationship. A "reactive" immune mechanism, triggered by a parasite located at a distant site, appears to be responsible for this type of arthritis.