Late presentation of pulmonary aplasia in an elderly male: a case report

The term ‘agenesis’ was coined to mean the failure of all or part of an organ to develop during embryonic growth. Agenesis of the lung is an extremely rare congenital anomaly. The condition was discovered accidentally at the autopsy of an adult female in 1673 by De Pozze (1). The first case of left sided pulmonary agenesis was reported from India by Muhamed in 1923, in a medicolegal autopsy. Lung agenesis and aplasia are rare congenital conditions with a cumulative incidence ranging from 0.0034% to 0.0097% (1). When a patient has a radiopaque hemithorax, pulmonary agenesis or aplasia should be considered as a possibility, along with other frequently occurring conditions.

A 65-year-old male patient, a farmer by occupation, presented to us with complaints of exertional breathlessness for 1 year and associated swelling of both the lower limbs for 8 months. The breathlessness was initially of grade 1 modified Medical Research Counci (mMRC), which progressed to grade 2 mMRC over the last 6 months. He was a current smoker with 40 pack-year with no other co-morbidities. He denied a history of chronic respiratory symptoms either in childhood or before this presentation. Physical examination revealed a flattened left hemithorax with ipsilateral tracheal shift and reduced chest movements on the same side. There was a dull note on percussion. Absence of breath sounds on the left side, loud P2 and apansystolic murmur in the tricuspid area were appreciated on auscultation. Chest radiograph revealed a homogenous opacity in the left lower zone and non-homogenous opacity in the left upper and mid zone, along with mediastinal shift to the same side and associated rib crowding (Figure 1). A provisional diagnosis of left lung collapse was made. Since the 2D echocardiogram done showed dilated right-sided chambers, with disproportionately high pulmonary artery pressure, a Computed Tomography (CT) pulmonary angiogram with High Resolution (HR) cuts was performed. There was no evidence of acute or chronic pulmonary thromboembolism, but an abrupt cut-off of the left main bronchus was noted along with an absence of the left lung and left pulmonary artery, and compensatory hyperinflation with herniation of the right lung to the left (Figure 2), thereby explaining the non-homogenous opacity on the chest radiograph. The possibility of left lung aplasia was thought of, and a diagnostic bronchoscopy was done, which showed the left main bronchus ending in a blind loop (Figure 3). Multi-disciplinary discussion was done, and a final diagnosis of left pulmonary aplasia was made. The patient was managed with antibiotics, diuretics and bronchodilators. He was discharged with advice for vaccination and pulmonary rehabilitation on further follow-up.

Figure 1:

Chest radiograph showing homogenous opacity in the left lower zone with shifting of the mediastinum to the left.

Figure 2:

CT pulmonary angiography. (A) In the lung window below the level of the arch of the aorta, the left lung is not visualised with a shift of mediastinum to the left with compensatory hyperinflation of the right lung. (B) Tracheal division is seen with abrupt cut-off of the left main bronchus. (C) In mediastinal window at the same level shows the pulmonary trunk with the absence of branching on the left side. (D) Left pulmonary vasculature is not seen with a normal right main pulmonary artery.

Figure 3:

Bronchoscopy: Carina is dividing into left main bronchus and right main bronchus, but the left main bronchus is ending in a blind loop, and no openings are seen.

Unilateral lung agenesis occurs in different degrees of severity and most cases are associated with other congenital abnormalities, such as cardiac malformation, pulmonary artery atresia and tracheoesophageal fistula. It occurs predominantly in males, with the left side frequently being affected (2). Schneider in 1912 primarily classified agenesis into three groups, which were later modified by Boyden. Depending upon the stage of development of the primitive lung bud, pulmonary agenesis is classified into three categories (3): Type I (Agenesis):

Complete absence of lung and bronchus, and absence of blood vessels on the affected side.

The age of onset of symptoms in pulmonary aplasia is variable. In most cases, this anomaly is discovered during infancy because of recurrent chest infections or coexisting major congenital anomalies of other organs. However, patients with one lung have been reported to survive well into adulthood without much complaints and may present either incidentally or with a late complication like cor-pulmonale as in our case (4). Respiratory symptoms are similar and non-specific to most of the lung pathologies. The chronicity of symptoms, appearance in early childhood rather than new onset in late adulthood, will point to the possibility of a congenital anomaly. However, if the symptoms are of recent onset, as in our patient, the possibility of aplasia will be considered to be rare and may delay the diagnosis. On the chest radiograph, aplasia presents as a homogenous opacity of the affected hemithorax with compensatory hyperinflation and herniation of the opposite lung. In patients presenting with an opaque hemithorax with a mediastinal shift to the same side on a chest radiograph, the differential diagnosis in adults includes lung collapse secondary to endobronchial obstruction due to foreign body or malignancy, post-infectious atelectasis, fibrothorax, unilateral congenital developmental disorders of the lung, such as pulmonary agenesis and pneumonectomy. Absence of history of previous thoracic surgery, thoracotomy scar on chest wall, absence of rib resection and surgical staples in the abruptly terminated bronchus on chest radiograph will rule out a possible post-pneumonectomy status (5). Absence of prior respiratory symptoms or history of being treated for any pulmonary infections, including tuberculosis in the past, makes post-infectious sequelae very unlikely. Absence of cough, haemoptysis, loss of appetite and weight makes the possibility of collapse secondary to endobronchial lesion, including malignancy, less likely. However, to rule out malignancy, which is more common in the elderly with significant smoking history and recent onset of respiratory symptoms, further evaluation with CT thorax and bronchoscopy is needed. CT thorax can help rule out post-infectious atelectasis, fibrothorax and a lung mass, and can very well detect the absence of lung parenchyma along with abrupt cut-off of the bronchial tree on the affected side in a case of aplasia. Though CT thorax usually suffices, a CT pulmonary angiogram may be rarely required to confirm the absence of ipsilateral pulmonary artery and also rule out pulmonary thromboembolism in the presence of severe pulmonary hypertension and cor-pulmonlae as in our patient. Bronchoscopic examination can be contributory by revealing the main bronchus terminating in a blind-ending pouch and also rule out any co-existent infections or an endobronchial growth (6). The exact aetiology of pulmonary aplasia remains unknown, but may be associated with genetic factors, such as the duplication of the distal part of the upper arm of chromosome 2, intrauterine viral infections, exposure to ionising radiation or vitamin A deficiency (7). Hence, management of complications like cor-pulmonale, prevention of repeated infections of the single lung, dyspnoea relief and optimisation of exercise tolerance to ensure good quality of life will be the goal during long-term follow-up in such cases. The prognosis of pulmonary aplasia varies, with a mortality rate of 33% during the first year of life and 50% in the first 5 years. However, if a patient survives the first 5 years of life, a normal life can be expected without major complications. The prognosis depends on multiple factors, including coexisting congenital malformations, repeated infection of the normal lung and its complications like pulmonary arterial hypertension (2). The oldest patient cited to date is a 90-year-old woman presenting with ischaemic colitis with incidental diagnosis of aplasia of left lung (8). Our case is probably the oldest case of pulmonary aplasia to be reported from India to date.

Pulmonary aplasia is a rare condition that can sometimes present late in adulthood. In an adult presenting with an opaque hemithorax on chest radiograph, pulmonary agenesis/aplasia should be considered as a possible differential diagnosis. CT thorax is the investigation of choice for establishing the diagnosis of pulmonary aplasia. However, a CT pulmonary angiogram and bronchoscopy may be mandated for further evaluation and confirmation by excluding other possible clinical entities, especially in a case presenting late in adulthood with recent onset of respiratory symptoms.