This neonate has presented with acute respiratory distress and an oxygen saturation of 92%; the first priority should be stabilization via high-flow oxygen and propping him up, followed by careful monitoring. Given the history of a recent upper respiratory tract infection in a sibling, bronchiolitis and pneumonia are the most likely candidates for the causative etiology. However, when dealing with dyspnea in this age group, there are a few other uncommon but important conditions which should be kept in the back of one's mind - these include pneumothorax, congenital diaphragmatic hernias and congenital lung malformations. Examination shows marked subcostal recessions bilaterally, which is a feature of respiratory distress. Note also the presence of diminished breath sounds in the left side - this hints that the pathology is likely in the ipsilateral lung. Unfortunately, tracheal deviation is extremely tricky to assess in neonates - in older individuals, this can provide additional information helpful in localizing the lesion. There are no crackles or wheezes in the lung fields, which makes both bronchiolitis and pneumonia less likely; however, note that this does not definitively exclude these diagnoses. A chest x-ray is a good investigation at this point; this reveals a surprising finding: a grossly inflated left upper lobe displacing the mediastinum towards the opposite side, and apparently compressing the right upper lobe. This peculiar appearance is highly suggestive of congenital lobar emphysema (CLE), a rare condition where there is hyperinflation of one or more pulmonary lobes. However, note that localized pulmonary interstitial emphysema can also mimic these findings, as can pneumothorax. Thus a follow up CT scan of the thorax is essential; this confirms the presence of hyperinflation of the left upper lobe. An echocardiogram is also important in these patients, as up to 14% of children with CLE have associated cardiovascular abnormalities. Fortunately, the test findings are normal here. Surgical resection of the affected lobe will provide definitive cure; this should be performed as soon as possible as this is a severe presentation of CLE. While many pediatric units have a policy of administering IV antibiotics empirically as soon as a pneumonia is suspected, it is important to note that there are no clinical findings which would justify this in the current patient under consideration.
Congenital lobar emphysema (CLE), also known as infantile lobar hyperinflation or over-inflation, is a rare developmental anomaly of the lower respiratory tract, characterized by hyperinflation of one or more of the pulmonary lobes. The incidence ranges from 1 in 20,000 births to 1 in 30,000 births, with a male:female ratio of 3:1. In many cases, the underlying pathophysiology is unclear. However, in around one-quarter of all cases, obstruction of the developing airway via a "ball-valve" mechanism is believed to play a role; the resultant progressive air trapping results in hyperinflation of the affected lobe and a mass effect that compresses the remaining lobes and causes a mediastinal shift, with subsequent hemodynamic changes. Know obstructive causes include 'intrinsic' disorders of the lung such as developmental deficiency of bronchial cartilage, or 'extrinsic' causes such as vascular anomalies or intrathoracic masses. The left upper lobe is most often affected (40% to 50% of cases); this is followed by the left middle lobe (30% to 40%) and right upper lobe (upto 20%). Note that CLE usually affects only a single lobe. One third of all patients are symptomatic at birth, 50% are diagnosed in the first month of life and nearly all by six months of age; however, note that the rare patient can remain asymptomatic for years. The spectrum of symptoms may range from complete asymptomaticity, to severe respiratory distress and cyanosis. The severity depends upon the size of the affected lobe, the degree of compression of surrounding lung tissue, and the extent of mediastinal shift. Respiratory distress is the commonest mode of presentation; most present with moderate dyspnea in the first days of life, which may associated with wheezing, grunting respiration and tachypnea. This may progress on to cyanosis within days. Recurrent pneumonia and failure to thrive are less frequent presentations that may occur in milder forms of the disease. Physical examination typically reveals decreased breath sounds over the involved lobe. The cardiac apex may be displaced if marked mediastinal shift is present. In many cases, the diagnosis of CLE can often be made from its characteristic appearance on a chest radiograph. Classical findings are a hyperinflated lobe compressing neighbouring lobes and herniating across the anterior mediastinum to cause mediastinal shift. A CT chest is also essential, as this allows evaluation of bronchial obstructions and anatomical changes, thereby defining the limits of the affected lobe and indicating the location of its blood vessels (which is mandatory prior to surgery). Note that bronchoscopy, angiopulmography, ventilation/perfusion lung scans and barium esophagography may also be performed, but are usually not required. As 14% of children with CLE have associated cardiovascular abnormalities, echocardiography should also be performed once the diagnosis has been established. It is also possible to diagnose CLE in the antenatal period via fetal screening and obstetric monitoring with ultrasonography; the disease can be distinguished from other lesions by differences in echogenicity and reflectivity. Studies have concluded that surgical resection of the affected lobe is appropriate in all infants less than 2 months of age and in those over 2 months with severe respiratory distress, significant findings on CXR or abnormal bronchoscopy findings. Asymptomatic, or minimally symptomatic patients can be managed conservatively. In over 85% of cases, the long term outcome after surgery is excellent with complete cure; following surgery resolution of symptoms usually occurs within 48 hours.