Congenital pulmonary airway malformation (CPAM) presenting as spontaneous pneumothorax in young boy

Abstract

Congenital pulmonary airway malformation (CPAM) is most common congenital lung anomaly of lower respiratory tract accounting for approximately 25% of all congenital pulmonary malformations. It is usually unilateral and involves single lobe of lung. It is usually diagnosed prenatally; rarely found in children and adults. We report a rare case of 14-year-old male presented with sudden onset breathlessness secondary to right sided pneumothorax associated with right lower lobe cystic lesion; successfully managed with multidisciplinary approach involving tube thoracostomy and non-anatomical wedge resection of right lower lobe cystic lesion (using VATS). Adults diagnosed with CPAM usually present with breathlessness, fever, recurrent pulmonary infection, pneumothorax, and haemoptysis. For definitive treatment of symptomatic CPAM cases, surgical resection at the time of diagnosis is recommended in view of possible risk of malignant transformation and recurrent respiratory tract infections. Considering the mild but definitive risk of malignancy, it is advocated to closely monitor the individuals with CPAM even after the surgical resection.

INTRODUCTION

Spontaneous pneumothorax is very rare in children compared to adult population. The incidence of spontaneous pneumothorax in childhood age group is 4 per 1,00,000 children/year with male to female ratio of 2-4:1.^[1] CPAM, previously known as congenital cystic adenomatoid malformation (CCAM), is a rare developmental anomaly of the lower respiratory tract that replaces lung tissue with nonfunctioning cystic tissue. The incidence of CPAM is reported as 1 in 10000 to 1 in 35000 births.^[2] Congenital airway malformation can be misdiagnosed as pneumonia, congenital diaphragmatic hernia, pneumatocele, tuberculosis, and pneumothorax.^[3] It may manifest in the form of repeated infections but very rarely remains to be asymptomatic until its diagnosis.

CASE REPORT

14-year old male patient presented with chief complaints of dry cough, right side chest pain, breathlessness, and fever for past 8 days. He denied any past history of recurrent respiratory infections even in early childhood along with no significant family history of lung diseases. On physical examination, the patient was conscious and aware. He was afebrile, tachycardiac with a pulse rate 120 beats/min, tachypneic at 36 breaths/min, normotensive and O₂ saturation was within normal range. Trail’s sign was positive to left and right hemithorax was hyper-resonant on percussion and had decreased breath sounds on auscultation. Chest radiograph showed right-sided pneumothorax with mediastinal shift toward left [Figure 1a]. Routine investigations like hemogram, renal function test, and liver function tests were normal. Emergency right side small bore intercostal drainage tube insertion was done under local anesthesia; lung expanded immediately [Figure 1b]. In view of 14-year-old young boy, presenting with spontaneous pneumothorax causes of spontaneous pneumothorax in children such as Marfan’s syndrome, Cystic fibrosis, Neurocutaneous syndromes such as Tuberous sclerosis, Neurofibromatosis (NF-1), Birt-Hogg-Dube syndrome; congenital anomalies such as CPAM, Congenital lobar emphysema were considered as differential diagnosis. 2D-ECHO did not show features suggestive of Marfan’s syndrome. Pediatric rheumatologist’s opinion was to rule out Tuberous sclerosis and associated Lymphangioleiomyomatosis (TSC-LAM); advised ultrasonography (USG) of abdomen and pelvis (A + P) to rule out Angiomyolipoma of kidney and Ophthalmology opinion to look for retinal hamartomas. USG (A + P) was normal. There were no retinal hamartomas on ophthalmological examination. Markers like HMB45 and MELAN-A done on surgical specimen which turned out negative. Hence, considering the rarity of LAM in males along with negative markers; Tuberous sclerosis and Lymphangioleiomyomatosis were ruled out. Computed tomography thorax was done after 2 days which showed multiloculated air filled thin-walled cystic lesion measuring 2.6 × 1.9 × 2.8 cm in medial basal segments of right lower lobe consistent with congenital pulmonary airway malformation [Figure 2]. Thoracoscopic non-anatomic wedge resection for right lower lobe cystic lesion done using 45 mm endostapler with white reloads [Figures 1c and 3]. Histological examination showed cystically dilated spaces lined by flattened to ciliated columnar epithelium, reporting as Type-1 CPAM [Figure 4]. On follow up after 15 days, child returned to normal physical activity with no features of effort intolerance or respiratory distress.

Figure 1: Chest X-ray showing Right-sided pneumothorax with contralateral mediastinal shift (a), Right-sided ICD in situ (b) and Post-VATS resection and Post-ICD removal lung expanded on right side (c)

Figure 2: HRCT thorax showing multiloculated air filled thin-walled cystic lesion in the medial basal segment of Right lower lobe (2.6 × 1.9 × 2.8 cm) transverse section (a), Coronal view (b), and Sagittal view (c)

Figure 3: (a) Coronal view of follow up (3 months later) HRCT thorax showing postoperative small thin walled cyst with few atelectatic bands (Yellow arrow). (b) Coronal view of follow up HRCT thorax showing surgical Endo stapler (Green arrow). (c) Sagittal view of follow up HRCT thorax showing postoperative small thin walled cyst with few atelectatic bands (Yellow arrow)

Figure 4: (a) Histopathological examination shows presence of thin walled multilocular cyst filled with air and (b) cyst wall is lined by ciliated columnar epithelium (*)

DISCUSSION

Clinical presentation of CPAM can be variable as described in the literature. Most cases are seen in infants and neonates which usually presents with respiratory distress immediately following birth, although up to 50% cases can remain asymptomatic till adolescence or later in life.^[4-6] One of the review of literature found 9 asymptomatic cases among 45 cases (20%) aged from infants to 65 years old.^[7] Similarly another review of literature described in a case report showed 11 asymptomatic cases out of 42 (26%) identified cases of CPAM associated with only radiological abnormalities.^[8] Adult diagnosed CPAM usually presents with breathlessness, fever, recurrent pulmonary infection, pneumothorax, and haemoptysis. For definitive treatment of symptomatic CPAM cases, surgical resection at the time of diagnosis is recommended in view of possible risk of malignant transformation and recurrent respiratory tract infections. Our case presented with dry cough, right side chest pain at same location, breathlessness, and fever with chest radiograph suggestive of right-sided pneumothorax with left side mediastinal shift. Our case was successfully managed with Tube thoracostomy and Video assisted thoracoscopic surgery (VATS) with non-anatomical wedge resection of right lower lobe cystic lesion. Non-anatomical wedge resection is well-described procedure for a peripheral lung lesions that involve a minority of the lung lobe. Since no major bronchus or blood vessel was involved in the lesion, and the majority of the right lower lobe was healthy, there was no surgical indication for removing the entire lobe. Similar case was reported in USA in an 18 years old male diagnosed as left sided pneumothorax with past history of emergency left lower lobe resection for Type-I CPAM in neonatal period.^[5] Another CPAM case was presented in similar fashion with left-sided spontaneous pneumothorax in a 14 years old male patient in Syrian Arab population with radiological and histological examination suggestive of Type-II CPAM and managed with left posterolateral thoracotomy followed by surgical resection of left upper lobe.^[6]

There is a proven relationship between pneumothorax and undiagnosed CPAM cases.^[5] Our case presented with right-sided pneumothorax with contralateral mediastinal shift. Spontaneous pneumothorax secondary to underlying CPAM has been described in early infancy with atypical histological abnormalities.^[9] Two more cases with similar presentation who underwent surgical resection for a previously undiagnosed Type-I CPAM have been reported in 18-year-old patients, of which one male patient manifested with hemoptysis and hemopneumothorax and another female patient with pyopneumothorax.^[10,11] CPAM is diagnosed by CT scan or MRI of chest. In our case, CT thorax confirmed the diagnosis of CPAM. What makes our case noteworthy is the age of the patient, i.e. 14 years old, as almost all CPAM cases are diagnosed prenatally or during the neonatal period.

Congenital pulmonary airway malformations are hamartomatous lesions that involve increased proliferation and cystic dilatation of different parts of the airways such as cystic and adenomatous elements of tracheal, bronchial, and alveolar tissue.^[5] CCAM, now well known as CPAM, was originally reported in 1949 by Ch’In and Tang.^[4,12] In 1977, Stocker et al. proposed three predominant histopathologic types I-III and further extended into five categories from type 0 to type IV. Type I is the most common accounting for 60-70% of cases and is associated with cystic lesion up to 10 cm described as bronchial or bronchiolar type. Biopsy is often necessary to rule out malignant potential in adults presenting with CPAM.^[13] Cyst walls are lined by pseudostratified ciliated columnar epithelium and occasionally mucinous type.^[13,14] Pathologic findings in our case described presence of multiloculated air filled thin-walled cystic lesion in medial basal segment of right lower lobe (RLL) measuring 2.6 × 1.9 × 2.8 cm without any solid component in it and histological examination showing cyst wall lined by ciliated columnar epithelium [Figure 4]; thus diagnosed as Type-I CPAM. Histopathological examination also ruled out any evidence of malignancy. Peculiarly, proliferating LAM cells exhibit features of expressing melanocytic markers (HMB-45, Melan-A).^[15] In our case, it turned out negative. These patients have the most favorable prognosis as the lesions are usually resectable.^[5,13,16]

Few studies have emphasized the effectiveness of conservative management in selected CPAM cases.^[17] On the other hand, increased survival rates had been seen with surgical resection along with curative modality in neonates. In the absence of surgical resection, recurrent infections have posed as most common complication in first few years in an asymptomatic infants.^[18]

CONCLUSION

We report this case to enlighten the significance of considering CPAM as one of the differential diagnosis of cystic pulmonary lesions especially in children presenting with sudden onset of respiratory manifestations and to captivate toward spontaneous pneumothorax as a possible presenting symptom of CPAM cases in otherwise healthy individuals. HRCT thorax should be considered as initial diagnostic modality. Considering the mild but definitive risk of malignancy, it is advocated to closely monitor the individuals with CPAM even after the surgical resection. Follow up of all CPAM patients should include an evaluation for evidence of residual lung disease both with spirometric testing and chest imaging.

Abbreviations

CT = Computed Tomography,

CCAM = Congenital Cystic Adenomatoid Malformation

CPAM = Congenital Pulmonary Airway Malformation

HRCT = High Resolution Computed Tomography

ICD = Intercostal drainage

LAM = Lymphangioleiomyomatosis

MELAN-A = Melanoma Antigen

NF = Neurofibromatosis

RLL- Right Lower Lobe

TSC- Tuberous Sclerosis

VATS- Video Assisted Thoracoscopic Surgery

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.