rarely detected in the intrauterine life , lung agenesis is often discovered in childhood after repeated pulmonary infections , frequent hemoptysis , cardiorespiratory failure , or as part of polymalformative syndrome . here we report a case of a 20-year - old girl presenting a left lung agenesis discovered by a spontaneous pneumothorax . a 20-year - old girl was admitted to our hospital because of a brutal chest pain . physical examination revealed increased respiratory rate and absence of breath sounds on left of chest . a chest radiograph revealed a bilateral pneumothorax and a left basithoracic opacity [ figure 1 ] . the chest ct - scan revealed the absence of left main bronchus and left lung parenchyma , and the existence of a right lung hyperinflated crossing the midline with a corresponding pneumothorax [ figure 2 ] . a surgical pleurodesis was indicated for our patient because of a spontaneous pneumothorax occurring on a single lung . in per operative , by right thoracotomy , there was no left pleural cavity , a cardiac torsion and a herniated right lung presenting many blebs [ figure 3 ] . chest x - ray showing a bilateral pneumothorax , a left basithoracic opacity , and an abnormal cardiac silhouette chest ct - scan showing the absence of the left lung , a right lung crossing the midline with a corresponding pneumothorax , and a posterior push of the heart per - operative view by right thoracotomy . lung agenesis is an extremely rare malformation whose prevalence is estimated at 34 per million live births . the true incidence of this anomaly is unknown because 50% of cases are stillborn and more than 20% die at birth or during their first few months . right agenesis is rarer but more severe than the left , probably because of an excessive carina shift and an improper drainage of the functioning lung . lung agenesis is associated in 50 -75% with other malformations , especially cardiovascular , urogenital , gastrointestinal and osteoarticular ones . mortality is higher and earlier in these cases , generally within the first 5 years of life . type i ( agenesis ) : complete absence of lung , bronchus , and blood vessels to the affected side . type ii ( aplasia ) : existence of a rudimentary bronchus with complete absence of lung tissue . type iii ( hypoplasia ) : presence of variable amounts of lung parenchyma , bronchial tree , and supporting vasculature . our patient has been classified as type i. normal development of the lung begins in 26 day of intrauterine life from the foregut , and continues postnatally . a disturbance during the 4 week of gestation could cause an unequal division between the two lung buds resulting in a unilateral agenesis or hypoplasia . many factors were suggested to be responsible for this defect , such as consanguinity , deficiency of a vitamin , intrauterine infections , and environmental agents and drugs , but the exact etiology is still unclear . lung agenesis is often discovered in childhood after repeated pulmonary infections , or as part of polymalformative syndrome . a pneumothorax as a discovery circumstance has , to our knowledge , never been reported . the absence of lung parenchyma is not usually evident at the x - ray chest because of a controlateral upper lobe hypertrophy crossing the midline . the resulting image of basithoracic opacity may mimic lobar collapse , pleural effusion , or diaphragmatic hernia . the chest ct scan or mri is the clef of diagnosis . surgery is indicated in case of persistence despite drainage or incomplete lung re - expansion , first recurrence , or bilateral pneumothorax . first episode of spontaneous pneumothorax is also an indication for surgery when that affects a single lung . surgical treatment is not easy because of working on the functional lung that can not be conventionally excluded . several options may be used : low tidal volume ventilation , selective lobar isolation , a cardiopulmonary bypass or extracorporeal membrane oxygenation . in our case , we have opted for a conventional thoracotomy with low tidal volume ventilation , with a good outcome . tomomi reported a series of eight patients having unilateral pulmonary agenesis or aplasia with cardiac or tracheal associated malformations . in this series , intrahospital mortality after surgical repair exceeded 30% . successful pregnancy and survival to adult age ( up to 77 years ) are reported . lung agenesis is a rare but a serious condition which should be early diagnosed and followed up .
lung agenesis is a rare condition which prognosis widely depends on associated malformations . 
 clinical presentation is so variable and diagnosis is often made in childhood . here , 
 we present a case of a 20-year - old girl who was admitted because of a spontaneous pneumothorax . 
 explorations concluded at a left lung agenesis , a hyperinflated right lung crossing the midline with a corresponding pneumothorax . 
 there was no malformation else . 
 this congenital condition and treatment for this rare presentation are discussed in detail .