Echinococcosis is an infectious disease which in humans is caused by the larval stadium of two types of parasites (Echinococcus granulosus and Echinococcus multilocularis). It is most frequently localized in the liver, lungs and rarely in muscles. The parasite significantly affects the immune system of the host, which is why anaphylactic reactions are not rare, especially in cases of cyst rupture. This paper presents the case of a 53-year old woman who had urgent laparotomy on the presumed basis of rupture of ovarian tumour, with intra-abdominal haemorrhage and shock. It turned out to be echinococcosis of the iliopsoas muscle and anaphylactic reaction. The differential diagnosis of adnexal tumours should take into consideration echinococcosis as well. Symptoms of anaphylactic shock in the case of parasitic cyst rupture can easily be confused with the signs of haemorrhagic shock.