Ruptured hydatid cyst masquerading as tension pneumothorax.

We report a 35-year-old man who presented to us with features suggestive of a tension pneumothorax. However insertion of a chest tube did not result in any signs of improvement. Further investigation demonstrated that he had a ruptured hydatid cyst. He underwent an emergency thoractomy and excision of the cyst. Ruptured hydatid cyst should be considered as a possibility in patients who present with sudden onset respiratory distress and hypoxia in geographical areas where the disease may be prevalent.