Rare presentation of pneumothorax in a young woman with underlying congenital pulmonary airway malformation

Abstract

Congenital pulmonary airway malformation (CPAM) is the most common among a rare group of congenital anomalies of the lower respiratory tract. It has variable presentation depending on its subtype and the patient’s age. It may lead to respiratory distress in neonates. It can be a particularly challenging diagnosis in children born asymptomatic but present with complications later in life such as haemoptysis, recurrent chest infections, breathlessness and pneumothorax. Prenatal ultrasound, chest X-ray, CT scan and MRI are helpful in making a radiological diagnosis.

A woman in her late teens presented with shortness of breath and right pleuritic chest pain. CT’s chest showed a number of bullae of varying sizes on the right, including one huge bulla compressing all three lobes. She underwent lung volume reduction surgery via video-assisted thoracoscopy, and the histology specimen confirmed the diagnosis of CPAM type 1.

Background

Congenital pulmonary airway malformation (CPAM), which was previously known as congenital cystic adenomatoid malformation (CCAM), results from abnormalities of branching morphogenesis of the lung at various stages of development and may occur at different levels of the tracheobronchial tree. There is adenomatoid proliferation of bronchioles that form cysts instead of normal alveoli,¹ which can result in malformation with single or multiple cysts of uniform or various sizes.

CPAM is a hamartomatous condition but can also be associated with malignancies.^{2 3} It is important to explore the family history of cancers and cystic lesions as it can be part of the familial pleuropulmonary blastoma syndrome. CPAM can be life-threatening if not treated timely and appropriately. Therefore, creating awareness among adult respiratory physicians can potentially avoid late or misdiagnosis. CPAM diagnoses can be particularly challenging and easily overlooked, as pneumothorax, haemoptysis and recurrent chest infections are common presentations from a wide range of aetiologies.

We review a case of a young woman who presented with pneumothorax associated with CPAM type 1.

Case presentation

A woman in her late adolescence was seen in the community by a general practitioner with a 2-week history of shortness of breath on exertion. Chest X-ray was arranged as an outpatient, which showed a large right-sided pneumothorax (figure 1). She was, therefore, brought to accident and emergency department for management.

Figure 1.

Initial chest X-ray showing right pneumothorax.

She was anxious on arrival with no associated chest pain, fever, cough or haemoptysis. She had no medical history and was a non-smoker. Previously, she was asymptomatic and never had a chest X-ray. There was no antenatal ultrasound recorded in the patient’s notes. There was no history of trauma.

On examination, air entry was reduced on the right, and oxygen saturation was 100% on room air. She was tachypnoeic with a respiratory rate of 24 breaths per minute and tachycardic with a pulse rate of 101 beats per minute and had a temperature of 37.3°C. The rest of the physical examination was normal.

A small-bore right-sided 12 French intercostal chest drain was inserted via the Seldinger technique to treat symptomatic pneumothorax. However, there was a persistent air leak and chest X-ray did not show significant radiological improvement (figure 2). This prompted a chest CT, which revealed a huge bulla originating in the right lower lobe, causing significant compression of all three lobes, deviation of the mediastinum to the left and depression of the right diaphragm (figures 3 and 4). Despite the chest drain being in situ for a few days (figures 5 and 6), there was a small persistent pneumothorax in the right apex. She was, therefore, referred to the thoracic surgeons for video-assisted thoracoscopy (VATS). She underwent lung volume reduction surgery, and a pleural tent was undertaken. She had an excellent postoperative recovery.

Figure 2.

Chest X-ray post chest drain insertion.

Figure 3.

Axial view of chest CT with multiple bullae and compressed lung.

Figure 4.

Coronal view of chest CT showing compression effect of bullae on mediastinum and right hemidiaphragm.

Figure 5.

Axial view of chest CT showing bullae, compressed lung and small pneumothorax with an intercostal drain in situ.

Figure 6.

Coronal view of chest CT showing large bullae and a small pneumothorax with an intercostal drain in situ.

On macroscopic examination of the resected specimen, multiple bullae were noted, and some were ruptured. The largest bulla measured up to 75 mm. Microscopic analysis of the specimen revealed a large collapsed multiloculated cyst beneath the pleura. It showed fibrous tissue in the wall with patchy chronic inflammation and a partial residual lining composed of a single layer of ciliated columnar epithelium and focal low cuboidal cells. There was no mucinous epithelium or cartilage in the specimen. There was no evidence of malignancy. The overall picture was consistent with CPAM type 1. She had a normal abdomen and pelvis ultrasound, with no evidence of any cystic lesion in the kidney or liver.

Differential diagnosis

The main differential diagnosis of CPAM includes bronchopulmonary sequestration (BPS). CPAM can be differentiated from BPS as it receives its blood supply from the pulmonary circulation. In contrast, BPS has a systemic arterial supply and does not have a connection with the tracheobronchial tree.^{4 5} The macroscopic examination of the surgical specimen in our case did not reveal any feeding vessel from systemic circulation, which ruled out BPS."

A bronchogenic cyst is another differential of CPAM, and it appears radiologically as a single, non-air-filled locule and lacks communication with the bronchial tree. Histologically, it contains bronchial cartilage, smooth muscle and mucous gland.⁶ The lack of cartilage in the microscopic analysis of the resected specimen ruled out a bronchogenic cyst. Congenital diaphragmatic herniation was ruled out as there was no evidence of the presence of bowel loops within a hemithorax on CT imaging.

Outcome and follow-up

She had an excellent postoperative recovery, and the postoperative chest X-ray (figure 7) showed complete lung expansion. Long-term follow-up was decided on after a discussion in a multidisciplinary meeting. She had interval chest X-ray follow-up at one month (figure 8) and subsequent interval chest CT follow-up at eight months (figure 9), and three years which showed expanded lungs. There was no radiological evidence of any cystic lesion (figure 10).

Figure 7.

Postoperative chest X-ray showing lung expansion.

Figure 8.

Postoperative interval chest X-ray at 1 month.

Figure 9.

Postoperative, axial view of chest CT at 8 months showing expanded lungs with no cysts.

Figure 10.

Postoperative, axial view of chest CT at 3 years.

Discussion

CCAM is a rare cystic lung disease resulting from adenomatous hyperplasia of the respiratory epithelium.⁷ Stocker, in 1977, classified CCAM into three types based on morphological features. Type 1 CCAM includes single cystic lesions or multiple cysts of size greater than 2 cm. Type 2 CCAM was described as a multicystic lesion with a cyst size of less than 2 cm, and type 3 CCAM contains a solid mass. In 2002, Stocker revised the CCAM classification, and a further two types were added, and the name was also changed to CPAM.^{8 9} This classification included type 0, which is a solid tissue and involves both lungs, and type 4, which has a large cyst located in the periphery of the lung.¹⁰ Both types 0 and 4 are diagnosed in infancy.¹¹

CPAM occurs sporadically, and there is no genetic association except CPAM type 4 malformation, which can be associated with familial pleuropulmonary syndrome. The estimated incidence of CPAM is 1 in 25 000 to 35 000 pregnancies,¹² and it forms around 25% of all congenital lung lesions.¹³ CPAM has an equal prevalence in men and women and no racial predilection exists.¹⁴

Large lesions can impede normal alveolar development and growth due to the pressure effect. CPAMs have connections with the tracheobronchial tree. However, these connections are not normal. CPAM can arise in all lobes, and there is an equal distribution between the right and left lungs. The malformation is usually limited to one lobe, but it can also involve multiple lobes, and there is a tendency to involve lower lobes if presented during adulthood.¹

CPAM diagnosis in adults can be challenging as it is uncommon in the adult age group, and therefore imaging findings can be misinterpreted.¹⁰ Ultrasound is the best modality for diagnosing CPAM in the prenatal period; it is useful to delineate the anomaly’s morphology, echogenicity and blood supply. Further imaging, like contrast-enhanced CT and MRI, are used for further characterisation of the lesion and to differentiate it from other congenital anomalies before the surgery. Chest CT is a reliable imaging tool to diagnose and classify CPAM in adults.¹⁵ CPAM may present with complications after birth such as recurrent chest infections, pneumothoraces, haemoptysis and dyspnoea.¹⁶ CPAM can be associated with malignancies like pleuropulmonary blastoma, bronchoalveolar carcinoma and rhabdomyosarcoma.¹⁷

Our patient presented with a symptomatic pneumothorax, an uncommon presentation of a rare congenital anomaly. The British Thoracic Society (BTS) pleural guidelines recommend the use of a small-bore (<14 French) intercostal drain insertion via the Seldinger technique for the initial management of symptomatic pneumothoraces. However, if there is a persistent air leak or the lung fails to re-expand, other treatment options include converting the drain to a large bore, applying suction to the drain, autologous blood patching/chemical pleurodesis, endobronchial valves or thoracic surgery.¹⁸ BTS pleural guidelines emphasise seeking an early thoracic surgeon’s opinion as a preferred option if a patient is deemed fit for surgical intervention.

Our patient had an initial 12 French intercostal drain insertion to manage symptomatic pneumothorax, but in view of persistent air leak and failure of the lung to re-expand, a thorax CT was performed and showed multiple bullae. It is likely that one of these bullae ruptured, resulting in pneumothorax and persistent air leak. Following the chest CT and subsequent discussion with thoracic surgeons, the patient underwent lung volume reduction surgery with a pleural tent via VATS. Her postoperative recovery was uneventful. CT imaging, in conjunction with histology, confirmed the diagnosis of CPAM type 1. Potentially associated malignancies were ruled out by chest CT, histology of resected segment and ultrasound abdomen and pelvis. The patient is currently asymptomatic and has been followed up with interval imaging over the last 3 years. The lack of new cyst formation over this time on serial imaging can differentiate CPAM from other cystic lung diseases with pneumothoraces.

Patient’s perspective.

I initially visited my general practitioner when I realised I was getting very out of breath while going out for a run in the evenings. I had previously never had any obvious issues with this and was generally an active person, but for some reason, I found myself unable to complete my normal exercises, so I decided to make an appointment. Little did I know it was very lucky I did. It was initially thought I had asthma, but after going for an X-ray, it became clear this was not the case. The ambulance ride to the hospital from the X-ray department was a terrifying experience I will never forget. I found myself in utter shock and denial when I was told my lung was collapsed. I couldn’t understand how that could be the case when I was still up on my feet and seemingly okay.

It took some time and a lot of dedication from my amazing surgical team to uncover the cause of my ailment and come up with an appropriate plan for me. I will be forever grateful to the team for looking after me while I was living in the hospital for a month and putting me at ease whenever I felt scared.

Post surgery I had to do a lot of physical therapy and breathing exercises, which were the hardest parts of the day, but the amazing physios got me through. Since my surgery, I have found out what it is really like to have two working lungs. Little things like diving and holding my breath underwater I am now able to do; prior to this, I couldn’t hold my breath underwater but never thought about why this was the case. I am also able to go on hikes up mountains without feeling like my chest is on fire. Lastly, I recently had to do a respiratory test at work, and I’m happy to say I scored above average! The follow-up from the team has been amazing, and I am so grateful for the resolution.

Learning points.

• Congenital pulmonary airway malformation (CPAM) is the most common among a rare group of congenital anomalies of the lower respiratory tract.

• Diagnosing congenital anomalies in adults is often challenging and can easily be overlooked. We suggest including CPAM in a broad list of differentials in adult patients who present with pneumothorax, cystic lung disease, recurrent chest infection and/or haemoptysis.

• Early diagnosis of CPAM and timely intervention can potentially avoid life-threatening complications and improve quality of life. It is noteworthy that surgery can be curative.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).