Introduction:
Congenital airway lesions are a group of conditions where a part of the lung undergoes rapid abnormal growth or mass. The medical abbreviation CPAM refers to congenital pulmonary airway malformation. The content of the mass can either be filled with fluid or a solid mass. The symptoms may be mild to severe. The condition mainly affects the neonates and pediatric population known as congenital pulmonary airway malformation babies (CPAM babies). In CPAM babies, the condition mainly affects them during fetal development, and the lungs are abnormally developed. It is a rare developmental anomaly affecting several newborns.
What Is a Congenital Pulmonary Airway Malformation (CPAM)?
Congenital pulmonary airway malformation (CPAM) is the most common type of congenital airway lesion. It is a lung malformation that usually affects a single lobe of one of the lungs.
It forms during fetal development. It was previously known as congenital cystic adenomatoid malformation because it had cysts and glands in the lung. The cysts are continuous, with the airways filled with fluid in utero and, after birth, filled with air. The size of the lung mass can change throughout pregnancy; that is, it can grow, remain the same size or even regress.
What Is the Cause of Congenital Airway Lesions?
The exact cause is unknown. It is congenital, and the child is inborn with the disease. It is also unknown whether it is a developmental failure or a hamartoma, a benign overgrowth of tissue. Sometimes, it can prevent the growth of normal healthy lung tissues from developing, resulting in pulmonary hypoplasia, which is the underdevelopment of the lungs. Also, it can push on the heart or large veins, causing blood to back up in the fetal veins, and when this happens, fluid can leak into the fetal tissues, a condition known as fetal hydrops.
What Is the Pathophysiology of Congenital Airway Lesions?
The congenital airway lesion can arise from different parts of the tracheobronchial tree. Therefore, it has been subdivided into five types, resulting in distinct histopathological differentiation, clinical features, malignant potential, and prognosis.
Subdivisions:
Type 0:
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Acinar dysplasia.
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Arises from the trachea or proximal bronchus.
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Represents global arrest of lung development.
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Cysts are 0.25 inches in diameter and lined by ciliated pseudostratified epithelium, goblet cells, and bronchiolar cartilage.
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Involves all the lobes.
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It is the rarest form, seen in one to three percent of cases, and it is usually severe and lethal postnatally.
Type 1:
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Large cysts.
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Arises from the distal bronchus or proximal bronchiole.
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One or more dominant cysts of 0.75 to 3.94 inches in diameter. Smaller cysts may surround it.
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Cystic layers are thin and lined by ciliated pseudostratified epithelium with bronchiolar differentiation, mucinous cells in 33 percent, and cartilage in 10 percent of the cases.
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The most common type is seen in almost 70 percent of the cases.
Type 2:
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Cysts are less than 0.79 inches in diameter.
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Arises from the terminal bronchioles.
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Cysts are lined by ciliated cuboidal or columnar epithelium, and mucinous cells and cartilage are absent.
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Associated with other abnormalities such as renal agenesis, pulmonary sequestration, and congenital cardiac anomalies.
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Seen in 20 percent of the cases.
Type 3:
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Microcysts of less than 0.59 inches in diameter.
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Arises from the near alveolus.
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A cyst is lined by ciliated cuboidal epithelium, and mucous cells and cartilage are absent.
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Typically, it involves an entire lobe.
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Poor prognosis.
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Seen in 10 percent of the cases.
Type 4:
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Typically, it affects a single lobe.
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Arises in the alveoli are lined by alveolar epithelium.
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Cysts are large and can measure up to 3.94 inches in diameter.
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Associated with malignancy, specifically pleuropulmonary blastoma.
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It is not distinguishable from type 1 on imaging.
What Are the Symptoms of Congenital Airway Lesions?
It is usually asymptomatic. Symptomatic infants may present with respiratory distress due to compression of the airways.
The various types of congenital airway lesions may present with different clinical features, which are mentioned below:
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Type 0 - It is incompatible with life, and it is fatal.
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Type 1 - It presents with tachypnea (abnormal increase in heart rate) and cyanosis (bluish discoloration).
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Type 2 - It presents similarly with respiratory distress and other congenital anomalies such as renal agenesis, diaphragmatic hernia, and cardiovascular abnormalities.
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Type 3 - The mass can expand and transform from pulmonary hypoplasia to fetal hydrops.
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Type 4 - It is associated with lung cancer, such as bronchoalveolar carcinoma and pleuropulmonary blastoma, and recurrent infections, which can lead to pneumothorax and result in fluid accumulation within the pleural cavity.
How to Diagnose Congenital Airway Lesions?
The diagnosis of congenital airway lesions is as follows:
Radiographic Features:
Antenatal Ultrasound:
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It appears as an isolated solid intrathoracic mass, usually indicative of a type 3 congenital airway lesion, and is usually hyperechoic. It may also cause the heart to get displaced to the contralateral side.
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Partially cystic and partially echogenic masses are characteristic of type 1 and 2 lesions. The size of the two cysts distinguishes the two types.
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Hydrops fetalis, meaning edema of the fetus, and polyhydramnios may be detected on ultrasound as ancillary sonographic features.
Radiograph:
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Type 1 and 2 - It may show multicystic large air-filled lesions, which may cause a mediastinal shift, depression, and inverted diaphragm. Initially, the cysts may be completely fluid-filled because they may appear solid.
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Type 3 - It may appear as solid lesions.
Computed Tomography (CT):
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The most common findings are areas of small cysts less than 0.79 inches in diameter, with other abnormalities like a larger cystic area, consolidation, or low attenuation.
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Multiple large cystic lesions of more than 0.79 inches in diameter are seen alone or with other abnormalities like areas of small cysts, consolidation, or low attenuation.
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Low attenuation areas are clusters of microcystins.
The advantage of doing a computed tomography over other diagnostic aids is that it more accurately delineates the lesion's location and extent. CT angiography also allows for identifying systemic arterial supply if present.
How to Manage Congenital Airway Lesions?
The treatment options are described below:
Treatment:
Surgical removal is the mainstay of treatment in symptomatic patients with respiratory compromise and recurrent infections. Type 1 lesions show the best prognosis. There is a need for supportive care of CPAM babies, including monitoring respiratory distress and providing oxygen support. If the condition is diagnosed and treated early, the prognosis is favorable.
What Are the Complications of Congenital Airway Lesions?
The postnatal complications are:
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Recurrent pneumothorax (lung collapse).
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Hemopneumothorax (pleural space is filled with air and fluid).
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Pyopneumothorax (pleural space is filled with pus and gas).
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Bronchoalveolar carcinoma (lung cancer).
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Bronchogenic carcinoma (lung tumor).
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Pleuropulmonary blastoma (lung cancer).
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Rhabdomyosarcoma (soft tissue cancer).
The postnatal complications are:
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Hydrops fetalis (presence of fluid in the organs and tissues of babies).
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Pulmonary hypoplasia (underdeveloped lung).
What Are the Differential Diagnosis of Congenital Airway Lesion?
The differential diagnosis includes:
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A bronchogenic cyst (abnormal tissue growth in the bronchial tree).
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Pulmonary sequestration (birth defect of lower respiratory tract).
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Congenital diaphragmatic herniation (birth defect of diaphragm).
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Congenital lobar emphysema (birth defect of lungs).
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Localized congenital cystic bronchiectasis (damaged airways from birth).
Conclusion:
Congenital pulmonary airway malformation, though rare overall, is the most common congenital airway lesion. It can be diagnosed early by the second trimester with the help of prenatal ultrasonography, leading to an overall decrease in the number of cases. Again, a multi-disciplinary approach to the care of CPAM babies will offer a better outcome.
