Abnormal Chest Radiograph in 8-Year-Old Boy With Asthma

An 8-year-old boy with mild persistent asthma presents to the emergency department (ED) for an acute asthma exacerbation in the setting of an upper respiratory tract infection for the last 4 days. He also has shortness of breath with increased work of breathing and chest tightness for 1 day with only mild relief with albuterol, prompting presentation to the ED.He was diagnosed with reactive airway disease at 6 months of age. Pulmonary function testing prior to presentation demonstrated mild obstructive lung disease and positive postbronchodilator response, confirming a diagnosis of asthma. He has had 2 prior hospitalizations for bronchiolitis responsive to albuterol and oral steroids as an infant and 1 for left upper lobe (LUL) pneumonia 3 years prior to current presentation. He has required 3 oral steroid courses in his lifetime. He has no prior intensive care unit admissions and has never been intubated for his asthma. He was started on a daily low-dose inhaled corticosteroid (ICS) at 6 months of age, and a leukotriene inhibitor was added to his regimen at age 3 years. Because of worsening symptoms at 6 years old, he was increased to a medium-dose ICS, which initially led to clinical improvement. However, in the last year, his symptoms have worsened again, and he now wakes up with cough at least 3 nights per week and tires more easily with exertion. He is currently using a beclomethasone 40-mcg inhaler twice daily and 5 mg montelukast nightly. His asthma triggers include upper respiratory tract infections, which often lead to a prolonged cough, as well as weather changes and exercise. Home environmental exposures are positive for roaches and mice in the home. He otherwise had normal growth and development.In the ED, he is afebrile with normal blood pressure for age and O2 saturations on room air. On physical examination, he is noted to be in moderate respiratory distress with tachypnea and subcostal retractions. Auscultation of lungs reveals diffuse biphasic wheezing with decreased breath sounds on the left. He is also found to be tachycardic but otherwise with normal heart sounds. Skin is otherwise warm and well perfused with no digital clubbing noted. Chest radiograph (CXR) (Figure 1A) is obtained and demonstrates a large hyperlucency in the left mid and upper lung corresponding to the area of opacification found on CXR when the patient had prior pneumonia along with an adjacent dense rounded structure. Bedside ultrasonography reveals no pneumothorax. His respiratory status improves with decreased wheezing and work of breathing after a dose of dexamethasone and 3 treatments with combination albuterol/ipratropium nebulizers, and he is discharged home. He is referred to the pulmonary clinic for follow-up given the abnormal CXR findings in the setting of poorly controlled asthma.The differential diagnosis for this patient encompasses several congenital, infectious, and neoplastic disorders.The large hyperlucency of the left upper lung corresponds to the area of opacification on CXR when this patient was diagnosed with LUL pneumonia. The resultant hyperlucency may represent a pneumatocele, although pneumatoceles are often more rounded and cystic rather than causing lobar hyperinflation. Furthermore, pneumatoceles often appear within the first week of infection and have usually resolved by 4 weeks to 6 months after the infection.1 Children with pneumatoceles are also often asymptomatic, making this diagnosis less likely in this symptomatic patient presenting 3 years after his initial infection.The dense rounded structure seen adjacent to the hyperlucency on CXR may represent a bronchogenic cyst. However, bronchogenic cysts are not usually associated with hyperlucency, as seen on imaging with this patient. Bronchogenic cysts may cause bronchial compression leading to some emphysematous changes, but such cysts are often seen in the mediastinum, unlike with this patient.2The emphysematous changes could also represent congenital lobar overinflation, especially given the patient’s early hospitalizations as an infant. However, nearly half of affected patients are symptomatic at birth with retractions, wheezing, cyanosis, and difficulty in feeding.3 This patient was asymptomatic at birth and otherwise had an uncomplicated immediate postnatal course. Additionally, on CXR, the affected lobe often appears opaque in the immediate postnatal period in a diffuse reticular pattern because of fetal lung fluid retention with overinflation and hyperlucency of the affected lung within the first 6 months of life.3 While the patient does not have a neonatal CXR for comparison, CXR at 6 months old (Figure 1B) showed clear lungs with no hyperlucency and was initially read as normal, with hyperlucency of the left lung not developing until later in life (Figure 1A).The hyperlucency on chest radiograph may also represent multicystic lesions that may not be well delineated. A radiograph with multicystic, air-filled lesions is consistent with congenital pulmonary airway malformations (CPAMs). While this patient’s initial radiographic findings may be consistent with CPAM and the patient had progressive respiratory distress that can be seen with CPAM, the diagnosis is usually made on antenatal ultrasonography or in the neonatal period with completely or partially fluid-filled cysts, which was not seen with this patient.4The patient’s atopic symptoms and recurrent chest infections are also consistent with allergic bronchopulmonary aspergillosis. However, the patient was not sensitized to Aspergillus on further allergic testing, making it less likely.The patient’s radiographic findings could also have represented a wide array of benign and neoplastic endobronchial lesions, although this is unlikely given the patient’s clinical picture. Primary malignant endobronchial lesions, such as bronchogenic adenocarcinoma and small-cell carcinoma, are exceedingly rare in the pediatric population, and this patient otherwise did not exhibit hemoptysis or any constitutional symptoms, such as fever, weight loss, or malaise.5 Similarly, while benign endobronchial lesions, such as endobronchial hamartomas, may present on imaging with atelectasis or hyperinflation due to partial occlusion of an airway, they are most common in the sixth and seventh decades of life.6Chest computed tomography (CT) (Figure 1, C and D) demonstrated segmental pulmonary emphysema with diminished vascularity and several central cystic lesions in the LUL, which may correspond to the dense rounded structure on prior CXR (Figure 1, A and B). The LUL apicoposterior and anterior segmental bronchi were not visualized. The cystic lesions found on chest CT likely represent bronchoceles, which can form as a result of localized obstructive emphysema secondary to inflammatory narrowing of a bronchus. The emphysematous changes initially seen on CXR in combination with bronchocele formation confirmed on chest CT were consistent with a diagnosis of bronchial atresia.Bronchial atresia is a rare congenital airway abnormality resulting from a focal interruption of any bronchus. The exact pathophysiology of bronchial atresia is not well known, but it has been proposed that the focal bronchial interruption is likely as a result of an antenatal vascular insult.7–9 The atretic bronchus does not communicate with the central airway, so it often becomes impacted with mucus and subsequent aeration occurs via collateral channels, leading to bronchocele formation with surrounding lobar hyperinflation. Most cases are asymptomatic and are diagnosed in the second or third decade of life.9,10 However, some affected patients can develop recurrent chest infections, persistent dyspnea, or hemoptysis, which can present at any age.10 CT scan remains the imaging modality of choice to confirm a diagnosis of bronchial atresia because it can differentiate bronchocele formation from other causes of mucoid impaction, and it can clearly delineate air trapping and emphysematous changes.9There are no consensus guidelines regarding conservative management with yearly clinical assessment and serial imaging to monitor symptoms vs immediate surgical intervention for bronchial atresia. Some advise initial conservative treatment with surgery reserved for patients who develop complications secondary to the atretic bronchus, such as recurrent chest infections, persistent dyspnea, or hemoptysis.10 Others advise lobectomy to prevent the development of complications, especially in the younger patient who has the capacity for compensatory lung growth and is relatively healthier to better tolerate the procedure.8,11,12Our patient had poorly controlled asthma, progressive shortness of breath, 2 prior episodes of bronchiolitis, and previous LUL pneumonia. Thoracoscopic left upper lobectomy was advised, and he tolerated the surgery without complications. Pathology of the LUL demonstrated respiratory bronchioles filled with mucus, macrophages, inflammatory cells, and dilated alveoli, compatible with bronchial atresia.He initially recovered in the pediatric intensive care unit with a chest tube removed on post-op day 3, and he was discharged on post-op day 4. One month post-op, the patient and mother noted fewer coughing episodes as well as nighttime cough or awakenings. His asthma remains well controlled on his current regimen, with no acute asthma exacerbations or respiratory illnesses requiring hospitalization in the last 2 years. As a result, it can be concluded that his poorly controlled asthma was likely exacerbated by his underlying bronchial atresia, as symptoms improved postoperatively.Baseline CXR in patients with poorly controlled asthma and serial imaging in those with persistent abnormal CXR can help identify an underlying anatomical pulmonary diagnosisSurgical intervention to treat symptomatic bronchial atresia may alleviate symptoms and help to prevent serious future complications