Abstract
Introduction: Pulmonary agenesis is an extremely rare congenital pathology which is defined as the complete absence of lung parenchyma, its corresponding bronchus and pulmonary vessels. Its estimated prevalence occurs in only 24 of 1,000,000 live births. As of date, the exact etiology is still not known but could be possibly linked to genetic factors, viruses and vitamin A deficiency in pregnancy. Clinical manifestations which may suggest the diagnosis include neonatal respiratory distress shortly after birth and recurrent respiratory tract infections during childhood.
Case presentation: A 7-month-old male infant presented with fever, cough, severe respiratory distress and peripheral cyanosis 12 hours from birth. He was diagnosed and managed a case of neonatal pneumonia at a tertiary hospital and was discharged stable. On the interval, the child presented with recurrent episodes of pneumonia. After further diagnostic evaluation at this institution, he was diagnosed with complete right pulmonary agenesis with patent ductus arteriosus, tracheal stenosis and a dextroposed heart . During the hospital stay, the patient eventually expired due to severe sepsis secondary to pneumonia.
Discussion: Pulmonary agenesis is a life threatening condition causing increased susceptibility to infections with a mortality rate as high as 50% in the 1st year of life. Anatomically, there may be maldevelopment of cilia and bronchial cartilages which may cause poor drainage of tracheobronchial tree secretions and promote reservoir for infection. The disease entity is associated with multiple congenital anomalies which may further aggravate the disease, the most common being cardiac in nature.
Conclusion: The diagnosis of pulmonary agenesis must always be entertained in patients presenting with recurrent respiratory infections and a persistently opacified hemithorax with mediastinal shift on diagnostic imaging to reduce mortality and improve prognosis.
Key words: pulmonary agenesis, dextroversion, patent ductus arteriosis, x-ray, CT- scan, diagnosis, infant
Introduction
First reported in 1673 by De pozze1, pulmonary agenesis is an extremely rare congenital anomaly defined as the complete absence of lung parenchyma, its corresponding bronchus and pulmonary vessels due to disruption of embryologic lung development . According to Dinamarco and Ponce2 (2015), the estimated prevalence of pulmonary agenesis is only 24 out of 1,000,000 live births with majority only being discovered upon autopsy. A study by Booth and Berry3 (1967), shows that less than 200 cases of pulmonary agenesis have been reported worldwide as of present. In the search for literature, we found only 5 cases of pulmonary agenesis with patent ductus arteriosus and 2 cases of pulmonary agenesis with PDA and tracheal stenosis. Locally, only 2 studies of pulmonary agenesis were retrieved.
Pulmonary agenesis is unilateral at presentation with predilection for the left lung. As of date, there is no preference for gender and no exact etiologic factor is known. Clinically, most common presentation is neonatal respiratory distress few hours after birth with recurrent episodes of pneumonia during childhood. The disease entity is frequently associated with other congenital abnormalities, most commonly cardiovascular in nature. If there is no other congenital anomaly present, patients with unilateral pulmonary agenesis may live normal lives but are at increased risk for severe respiratory infections, which may be associated with high mortality rates if not diagnosed early on. The diagnosis should be considered when radiographic examinations show an opacified hemithorax with marked displacement of the heart and other mediastinal structures without evidence of atelectasis or fibrothorax (Lukas, et al., 1953)4. CT scan imaging may be done to confirm the absence of lung parenchyma, its corresponding vessels and to evaluate for presence of other congenital malformations. With difficulty, pulmonary agenesis may be discovered during prenatal ultrasound screening.
Case report
A 7 month old infant was born preterm by 36 weeks to a 31 year old gravida 2 para 2 (2002) mother with no known significant maternal illnesses. The patient was born via spontaneous vaginal delivery with a birthweight of 3.15kgs, appropriate for gestational age, with good cry and activity. However at 12 hours of life, was noted to have respiratory distress. He was mananged medically at NICU for 10days as was treated as a case of neonatal pneumonia. He was discharged stable. On the interval, the patient was managed for recurrent respiratory tract infections. At 7 months of age, he was brought to the outpatient department due to cough and was given Salbutamol nebulizations, Cefalexin, and Prednisone as take home medications. Few hours after consult, patient was brought to the emergency room due to respiratory distress and unstable vital signs. Medical management was done however due to persistence of distress he was eventually intubated and hooked to a mechanical ventilator. Initial interpretations of the chest xray, showed pneumonia in the both lungs, CBC showed leukocytosis with neutrophilic predominace and reactive thromoboycytosis. Vital signs continued to decrease. Physical examination revealed an unresponsive cyanotic infant with harsh breath sounds and weak central and peripheral pulses. An initial diagnosis of sepsis secondary to pneumonia and dextrocardia with congenital heart disease was entertained. Upon transfer to this institution, the patient was stabilized, medical management was continued and diagnostic tests were carried out. Repeat chest-Xray was done and revealed homogenous opacification of the right hemithorax with ipsilateral shifting of the mediastinal shadow. Left lung was hyperaerated with prominent vascularity and transthoracic herniation (figure 1). 2D echocardiogram showed patent ductus arteriosus with 0.17-0.33 cm size with maximum SPG of 64 mmHg. Cardiac CT scan was eventually done revealing the following findings: (figures 2, 3 and 4) pulmonary agenesis of the right lung with associated dextroversion, pulmonary ductus arterisosus and an incidental finding of tracheal stenosis (figure 4). During the course of the hospital stay, the patient failed to improve. On the 117th hospital day the patient was noted with drop in vital signs and poor sensorium. Patient eventually expired due to severe sepsis secondary to pneumonia.
Discussion
Successful development of a functional lung involves multiple biochemical and physical processes. The process of lung growth starts to occur at the 4th-5th week of gestation and reaches maturity by the 36th week. Any pathologic insult to any level of lung development may cause disruption of pulmonary growth. The exact etiology of pulmonary agenesis has yet to be understood, however studies show that genetic factors, vitamin A deficiency in pregnancy, viruses and chromosomal abnormalities may play a roles in the pathogenesis of the disease. Schneider and Schwatbe 5 have classified lung agenesis into 3 groups (Table 1), with our patient classified as Type 1 due to the complete absence of right lung parenchyma, vessels and bronchus.
- Type I (Agenesis): Complete absence of lung and bronchus and absence of blood vessels to the affected side.
- Type II (Aplasia): Rudimentary bronchus with complete absence of lung tissue.
- Type III (Hypoplasia): Presence of variable amounts of lung parenchyma,bronchial tree and supporting vasculature.
Almost half of the cases diagnosed present with multiple congenital anomalies such as cardiovascular, musculoskeletal, genitourinary and gastrointestinal defects. The most common being cardiac congenital defects. A study done by Booth and Berry 6 (1976), tabulated 9 living patients with pulmonary agenesis with their corresponding cardiac anomalies, the most common being patent ductus arteriosus. The cardiac shunt is said to be possibly protective by its ability to act as a bidirectional shunt during attacks of severe hypoxia. Another incidental and rare finding upon CT scan was tracheal stenosis. Tracheal stenosis can be congenital in nature or be caused by extrinsic compression from the overstretched aorta due to displacement and narrowing of the mediastinal compartment.
Patients with lung agenesis are at increased risk for respiratory tract infections due to maldevelopment of cilia and tracheobronchial tree cartilages which may hinder proper drainage of the functioning lung and may act as a reservoir for infection.
With difficulty, this disease entity may be diagnosed early during the prenatal period by ultrasound and is visualized as a hyperechoic hemithorax with associated mediastinal shift. Radiographically, and similarly on CT imaging, patients with right pulmonary agenesis will show an opacified hemithorax with resultant displacement of the heart and mediastinal structures towards the affected side (Figure 1 ). There will also be dextroposed heart due to the inequality of pressures intrathoracically and resultant pulling of the mediastinal structures towards the affected side. Often herniation of the left lung across the mediastinum is seen as a compensatory mechanism of hyperaeration. On the side of agenetic lung, the posterior ribs may be narrowed in appearance due volume loss because of the absence lung parenchyma. Given the clinical history of respiratory distress, a radiographic differential for a white out lung with mediastinal shift would include complete atelectasis, diaphragmatic hernia and pulmonary agenesis/hypoplasia. Although agenesis of the lung is a very rare entity, it must always be entertained because it is life threatening and may cause mortality especially in the setting of infection.
Originally published 15.10.2019.