Ans. c. Congenital lobar emphysema (Ref: Nelson 19/e p1461-1462)The most likely diagnosis in a neonate presenting with respiratory distress with enlargement of left upper lobe of lung and mediastinal shift towards the right is congenital lobar emphysema.Congenital Lobar Emphysema (CLE)Congenital lobar emphysema (CLE) may result in severe respiratory distress in early infancy and may be caused by localized obstruction.Familial occurrence has been reported.In 50% of cases, a cause of CLE can be identified.Congenital deficiency of the bronchial cartilage, external compression by aberrant vessels, bronchial stenosis, redundant bronchial mucosal flaps, and kinking of the bronchus caused by herniation into the mediastinum have been described as leading to bronchial obstruction and subsequent CLE.Clinical Features:Clinical manifestations usually become apparent in the neonatal period but may be delayed for as long as 5-6 months in 5% of patients.Signs range from mild tachypnea and wheeze to severe dyspnea with cyanosisCLE affects the upper and middle lobes, with the left upper lobe the most common site.The affected lobe is essentially nonfunctional because of the over distention, and atelectasis of the ipsilateral normal lung may ensue.With further distention, the mediastinum is shifted to the contralateral side with impaired function seen as well.Diagnosis:A radiolucent lobe and a mediastinal shift are often revealed by radiographic examinationTreatment:Treatment by immediate surgery and excision of the lobe may be lifesaving when cyanosis and severe respiratory distress are present, but some patients respond to medical treatment.Some children with apparent congenital lobar emphysema have reversible over inflation, without the classic alveolar septal rupture implied in the term emphysema.