Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 9 1 2010 03 15 49 52 Soheil Ben Razavi Department of surgery. Division of pediatric surgery. Shaheed Sadoughi hospital, Yazd, Iran Mohammad Hassan Bemanian Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran Shokooh Taghipoor Department of pathology.Shaheed Sadoughi hospital, Yazd, Iran Reza Nafisi Moghadam Department of radiology.Shaheed Sadoughi hospital, Yazd, Iran Zahra Behnamfar Medical student, Shaheed Sadoughi University of Medical Sciences & Health Services, Yazd, Iran 2015 10 01 Difficult to treat asthma is an asthma syndrome that brings in our mind other differentials. Mediastinal masses are not common findings, but are important variables. Bronchogenic cyst is a congenital anomaly of the foregut that is typically found in the mediastinum and diagnosed accidentally. We present a 4-year-old girl with allergic asthma that began at 8-months of age and finally a bronchogenic cyst was detected in this patient. The patient had history of asthma since she was eight months old. She had a history of several asthma attacks which had partly responded to asthma management. During the last episodes of asthma attacks, she was hospitalized in Pediatric Intensive Care Unit. Imaging studies showed a 4×3 cm mass in the posterior part of the thoracic cavity that had led to tracheal narrowing was found for which the patient underwent thoracotomy and in surgical exploration a cyst that had compressed the thoracic trachea. Pathological examination of the cyst revealed a bronchogenic cyst. Bronchogenic cyst is an uncommon developmental abnormality but in a patient with obstructive pattern of airways it should be considered in differential diagnosis of asthma, especially if the asthma management is not successful. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/269 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/269/269