A Missed Late Presentation of a Congenital Pulmonary Airway Malformation as a Large Infected Bulla

Abstract

A congenital pulmonary airway malformation (CPAM) is a rare cystic anomaly that may occur during development of the fetal airways. The vast majority of CPAMs are detected in neonates; as such, it is unusual for diagnosis to occur in adulthood. We report a 21-year-old male patient who presented to the emergency department of the Hospital Ampang, Kuala Lumpur, Malaysia, in 2015 with chest pain, breathlessness and tachypnoea. Based on an initial chest X-ray, the patient was misdiagnosed with pneumothorax and underwent urgent chest tube insertion; however, his condition deteriorated over the course of the next three days. Further imaging was suggestive of infected bullae or an undiagnosed CPAM. The patient therefore underwent video-assisted thoracoscopic surgery, during which a large infected bulla was resected. A diagnosis of an infected CPAM was confirmed by histopathological examination. Following the surgery, the patient recovered quickly and no bullae remnants were found at a one-month follow-up.

A congenital pulmonary airway malformation (CPAM)—formerly known as a congenital cystic adenomatoid malformation—accounts for 25% of all congenital lung lesions.1,2 The vast majority of cases are diagnosed via ultrasonography during the immediate neonatal period.2 This report describes a rare case of CPAM first diagnosed in a young adult presenting with dyspnoea secondary to a large infected bulla. The patient was initially mis-diagnosed as having pneumothorax based on findings from a chest X-ray.

Case Report

A 21-year-old male patient with a history of smoking presented to the emergency department of the Hospital Ampang, Kuala Lumpur, Malaysia, in 2015 with chest pain, breathlessness and tachypnoea. On examination, the patient was tachypnoeic with reduced air entry in the left lung on auscultation. There was no recent history of acute illnesses or cough. His leukocyte count was 15,000/mm³.

A chest X-ray revealed a large lucency in the left hemithorax with depression of the left hemi-diaphragm and a mediastinal shift to the right [Figure 1]. This finding was initially misinterpreted as indicative of left-sided tension pneumothorax; as such, a chest tube was immediately inserted. However, the patient’s condition deteriorated over the following three days and he developed sepsis with coagulopathy. Repeat chest X-rays appeared to show non-resolving pneumothorax.

Figure 1.

Chest X-ray of a 21-year-old male patient with chest pain, breathlessness and tachypnoea showing lucency (arrow) with reduced lung markings in the left hemithorax and a corresponding increase in lung volume (arrowhead) evidenced by the contralateral mediastinal shift.

Computed tomography (CT) of the thorax revealed large air-filled lesions in the left upper hemithorax containing fluids and septations causing a mediastinal shift [Figures 2 and 3]. These findings were suggestive of an infected bulla, an undiagnosed CPAM or congenital lobar overinflation (CLO). Accordingly, the patient underwent left video-assisted thoracoscopic surgery (VATS), during which a large infected bulla was identified in the left upper lobe supplied by multiple vessels from the chest wall. The bulla was resected and a histological analysis confirmed a diagnosis of a CPAM with secondary infection [Figure 4A]. After the surgery, the patient quickly recovered following treatment with antibiotics and was discharged. At a one-month follow-up appointment, a chest X-ray showed no bullae remnants [Figure 4B].

Figure 2.

Post-chest tube insertion axial computed tomography scans of the thorax of a 21-year-old male patient showing an air-filled lesion with atelectasis in the left upper lobe (arrow). Note the tip of the chest tube (arrowhead) and the corresponding fluid level.

Figure 3.

Post-chest tube insertion computed tomography scans of the thorax of a 21-year-old male patient in the (A) sagittal and (B) coronal views showing a septated cystic lesion (arrows) replacing the normal left upper lobe.

Figure 4.

A: Haematoxylin and eosin stain at x100 magnification showing a cystic lesion lined by columnar epithelium. B: Postoperative chest X-ray of a 21-year-old male patient showing thickened left apical pleura (arrow) and the complete resolution of an ipsilateral upper lobe bulla.

Discussion

A CPAM is a hamartomatous lesion comprising both cystic and adenomatous elements of tracheobronchial and alveolar tissue and is characterised by intracystic communication with and connection to the tracheo-bronchial tree.2,3 The prevalence of CPAM has been estimated to be approximately one in 7,200 pregnancies.2 After birth, the lesions may regress, persist or remain stable.3 Stocker et al. first described three types of CPAM; however, more recently, these classifications have been expanded to five types reflecting developmental progression through the tracheobronchial tree, from the large airways to the bronchioles and alveoli [Table 1].4,5 An alternate classification of CPAM was proposed by Adzick et al., dividing CPAM cases into macrocystic, microcystic or solid lesions based on prenatal ultrasongraphy.6

Table 1.

Expanded classification of congenital pulmonary airway malformations5

Characteristic	Type 0	Type 1	Type 2	Type 3	Type 4
Frequency in %	1–3	50–65	20–25	8	10
Size in cm	≥0.5	2–10	<2–2.5	0.2–1.5	0.5–7
Location	Tracheobronchial	Bronchial/bronchiolar	Bronchiolar	Bronchiolar/alveolar duct	Distal acinar
Onset	Birth	Prenatal*	Postnatal	Prenatal*	Postnatal
Clinical presentation	Lethal pulmonary hypoplasia Absence or lack of alveoli	None (asymptomatic) Immediate or delayed respiratory distress or infection	Respiratory issues†	Development of hydrops in prenatal cases Respiratory distress‡ in postnatal cases	None (asymptomatic) Pneumonia or pneumothorax
Risk of malignancy	Unknown	Risk of bronchioloalveolar carcinoma	Unknown	Unknown	Risk of pleuropulmonary blastoma
Association with other congenital anomalies or conditions	Cardiovascular anomalies Renal hypoplasia	Unknown	Renal agenesis or dysgenesis Pulmonary sequestration Congenital cardiac anomalies	Unknown	Unknown

^*Particularly with large cysts.

^†These are often less significant than associated anomalies.

^‡Depending on the size of the cyst.

In most cases, CPAM presents in the neonatal period with acute respiratory distress and is characterised by unilateral lower lobe involvement.7 Diagnosis in adulthood is rare and can occur either as a result of infection, malignant transformation or discovered incidentally on chest X-ray.8 Adult patients with undiagnosed CPAMs can present with recurrent pneumonia, pneumothorax, bullae, haemoptysis or dyspnoea.7,9,10 The differential diagnosis in adults includes acquired cystic lesions (i.e. pulmonary tuberculosis [TB]) or congenital lesions (i.e. bronchogenic cysts and pulmonary sequestration).11,12 Other renal and cardiac anomalies may also be associated with CPAM. Pulmonary sequestration can be radiologically ruled out as this type of malformation has an anomalous systemic arterial supply, unlike CPAM.13 Histological analysis is crucial as this enables identification of the cause of the multicystic mass and excludes pulmonary TB.14

In the current case, a retrospective review of the initial chest X-ray indicated a large left-sided bulla causing a contralateral mediastinal shift; however, at the time, the bulla was mistaken for pneumothorax, resulting in the unwarranted insertion of a chest tube. Subsequently, CT scans revealed multicystic air-filled lesions, some of which contained fluid and enhanced the septa; at this point, CLO was suspected due to the unusual involvement of the left upper lobe. However, following VATS, a large infected bulla was identified and histologically confirmed to be a CPAM, likely type 1 as it occupied almost the entire left upper lobe.5 Radiology and histology ruled out pulmonary sequestration and pulmonary TB, respectively; however, an association with other renal and cardiac anomalies could not be excluded as this type of screening was not performed in the current case.

Among symptomatic infants with CPAMs, urgent surgical excision is usually advocated because segmental resection may be incomplete, resulting in recurrent infections or persistent pneumothorax.15–18 Among 19 surgically-treated infants and children, Pinter et al. reported respiratory infections and chest deformities occurring in seven and eight patients, respectively, over an average follow-up period of 7.7 years.18 However, in the current case, the patient underwent VATS dissection of the left upper lobe bulla. In such cases, the risk of recurrent infection-related complications is unknown as there is minimal published research regarding the long-term outcomes of adult patients with resected CPAM lesions. Nevertheless, most CPAM patients remain asymptomatic and otherwise healthy.16 Previous research has shown post-lobectomy lung volumes in asymptomatic CPAM patients to be 90% that of predicted normal values.19

Conclusion

The initial identification and presentation of a CPAM in adulthood is rare; as such, the diagnosis and treatment of such cases is challenging for unsuspecting clinicians and radiologists. Nevertheless, as many cases remain asymptomatic, the prevalence of adult CPAM may be under-reported. Long-term research is needed to assess treatment outcomes in adult CPAM patients.