Isolated left pulmonary artery hypoplasia

Pulmonary artery hypoplasia is a rare malformation of childhood that is usually associated with cardiac abnormalities. In the absence of these cardiac malformations it is discovered later when respiratory signs appear. It was a 56-year-old patient who had been referred for dyspnea with cough. The physical examination was normal. Chest X-ray, thoracic computed tomography (CT) scan and echocardiography suggested the diagnosis of hypoplasia of the left pulmonary artery without associated cardiac malformations. The early diagnosis of hypoplasia of the pulmonary artery allows the close follow-up of these patient and the planning of an adequate management.


Introduction
Unilateral pulmonary artery agenesis with lung hypoplasia is one of the rare congenital developmental anomalies of the lung. In fact, its prevalence was estimated at 1/200,000 [1]. There are no specific symptoms for this malformation. While some of the congenital lung lesions are diagnosed in neonates or in later periods of life, others are asymptomatic and may be diagnosed during the childhood or adult periods accidentally [2]. Prognosis depends on the extent of hypoplasia, what the underlying cause of the condition is and the presence of other congenital abnormalities. This condition is therefore managed in a number of different ways.

Discussion
Unilateral hypoplasia of a pulmonary artery (HPA) is caused by a malformation of the sixth aortic arch of the affected side during embryogenesis [1]. This congenital malformation is classified into two types which is as follows: (1) agenesis: proximal interruption of pulmonary arteries (PA); (2) hypoplasia: pulmonary arteries remained rudimentary. It has also been perceived that most of the cases affect the left PA [2]. This condition has been reported with a variety of cardiac malformations and usually presents with symptomatic disease.
The associated cardiac malformations include tetralogy of Fallot [3], atrial septal defect, coarctation of aorta, right aortic arch, and Eisenmenger's syndrome [4]. In the great majority of the cases in the literature, patients were diagnosed in infancy or childhood. In fact, only a limited number of patients appear to remain asymptomatic until adulthood [5]. In the case reported here, the patient had a left-sided pulmonary artery hypoplasia without the associated congenital cardiac anomalies which could explain the maintenance of an asymptomatic state.
According to previously published reports, presenting symptoms in adult patients can be variable such as exertional dyspnea or limited exercise intolerance (40%), hemoptysis (20%), recurrent pulmonary infections (37%) and pulmonary hypertension (25%) [6,7]. It has been proposed that hemoptysis could be caused by the collaterals arising from bronchial, subclavian, subdiaphragmatic and intercostal arteries which supplied the affected lung. On the other side, alveolar hypocapnia can cause bronchoconstriction, while impaired mucociliary clearance and diminished delivery of inflammatory cells may contribute to the high incidence of respiratory infections [8]. Chest X-ray of agenesis hypoplasia may give clue of the pulmonary agenesis. Usually, CT angiography confirmed the findings of CT. This test is suitable for evaluation of the collateral circulation, and also contributes greatly to treatment. In fact, in cases of repeated hemoptysis, this test is used to evaluate the collateral circulation, and the blood vessels responsible for this hemoptysis are embolized [9]. Pulmonary angiography remains the gold standard for diagnosis of vascular pulmonary malformations [10]. This invasive test imaging is not Page number not for citation purposes 3 usually performed in order to make a definitive diagnosis of hypoplasia PA. Perfusion scintigraphy can be also performed, it shows typically normal ventilation but no perfusion on the affected side. Other evaluation techniques, including cardiac catheterization and magnetic resonance imaging, have also been used to diagnose this condition.
However, as this case illustrated, a CT scan is quite useful in revealing the features of this disorder.
In addition, echocardiography should be performed in order to exclude cardiac malformations associated to this condition. In our case, this test reveals a pulmonary hypertension. Many patients with hypoplasia PA can remain asymptomatic for a long time, but the development of pulmonary hypertension may preclude long-term survival. In fact, the mortality rate of this condition remains 7%-8% [11]. Unfortunately, there are no guidelines or consensus regarding treatment. Surgical management can only be attempted in accompanying cardiac and vascular anomalies, in recurrent hemoptisis attacks, or in persistent lung infections and bronchiectasis [8]. Patients require close follow-up of pulmonary hemodynamics as well as continued medical management for pulmonary hypertension such as: calcium channel blockers, endothelin receptor antagonists and intravenous prostacyclin. Selective embolization of the collaterals may be done to control massive hemoptysis.

Conclusion
Left pulmonary artery hypoplasia is a rare congenital malformation.
Computed tomography is generally sufficient for definitive diagnosis.
Prognosis depends on many complications including mainly severe pulmonary hypertension and pulmonary hemorrhage.

Competing interests
The authors declare no competing interests.