The pathogenesis of IDPA remains incompletely understood. Assmann first suggested that abnormal differentiation of the arterial trunk during embryonic development could give rise to pulmonary artery dilation (3). A subsequently favored theory posits that defective development of elastic tissue within the pulmonary artery wall results in a focal weakness, predisposing the vessel to dilatation over time in response to normal hemodynamic forces (6). Support for this concept comes from case reports describing patients with concomitant hypoplasia or dilatation of the ascending aorta, which may indicate a generalized defect in arterial wall structure (7). While IDPA is often considered a congenital disease, it can also arise in association with other conditions, such as connective tissue diseases and genetic syndromes, highlighting the need for a thorough systemic evaluation in pediatric patients. Despite the enlargement of the pulmonary artery in IDPA, the vessel generally retains some elasticity, and patients typically demonstrate normal right ventricular and pulmonary pressures, with no significant chamber enlargement or wall thickening.

In the literature, most IDPA cases have been diagnosed in adulthood, although subtle or non-specific symptoms, such as mild dyspnea or cough, often date back to childhood but remain uninvestigated due to their benign nature (Table 1). Notably, Yang et al. (8) reported an antenatal diagnosis of IDPA, supporting the view that congenital factors are central to its etiology. However, acquired or secondary causes, including connective tissue disorders, vasculitides, and chronic pulmonary or cardiac conditions, must also be considered, especially in children with additional risk factors.

The classic criteria described by Greene et al. (1949) (3) for IDPA diagnosis are: (1) Simple dilatation of the main pulmonary artery (diameter >30 mm) with or without branch involvement, (2) Absence of abnormal intracardiac or extracardiac shunts, (3) Absence of chronic cardiopulmonary disease, (4) Absence of arterial vascular disease (e.g., syphilitic arteritis, atherosclerosis affecting the pulmonary artery).

Deshmukh et al. (1960) (1) added a fifth criterion: normal right ventricular and pulmonary artery pressures, defined as a pressure gradient <10 mmHg at rest and <15 mmHg on exertion. In pediatric practice, the interpretation of pulmonary artery diameter relies on z-scores, which account for age and body surface area, and a z-score greater than +2 is generally considered abnormal (9). Thus, pediatric-specific reference values are essential for accurate diagnosis and risk stratification.

Clinically, most patients with IDPA are asymptomatic (1), and the condition is often detected incidentally during imaging for unrelated complaints. When symptoms do occur, they are typically mild and include exertional dyspnea, chest tightness, or cough. Some patients may develop progressive right heart failure or cyanosis if the condition remains undetected for many years (Table 1), as highlighted by autopsy findings in rare cases (10). Hemoptysis, although uncommon, is the most concerning presentation, as it may herald dissection or rupture of the pulmonary artery—a potentially life-threatening event (11). However, available evidence indicates that such complications are extremely rare in children, and the overall prognosis for pediatric IDPA is favorable.

IDPA is considered a diagnosis of exclusion and primarily requires differentiation from diseases that can cause secondary pulmonary artery dilation (1). Two prominent mimics are pulmonary valve stenosis and pulmonary artery aneurysms.

The diagnosis of IDPA is primarily one of exclusion, and it is essential to distinguish it from other causes of pulmonary artery dilatation. Two important mimics are pulmonary valve stenosis and pulmonary artery aneurysms. Pulmonary valve stenosis can cause post-stenotic dilation of the pulmonary artery due to turbulent flow, with the dilation often taking on a sac-like or spindle-shaped appearance (12). Historically, it was thought that right ventricular pressure would be significantly elevated in these cases, but recent data show that right ventricular pressure can be normal, and even giant pulmonary artery dilatation can occur in asymptomatic patients—sometimes unrelated to the severity of stenosis (13). Furthermore, patients with pulmonary regurgitation may also exhibit right ventricular and atrial enlargement, as was observed in our patient. This underscores the need for a comprehensive assessment, as the presence of pulmonary regurgitation may confound the clinical picture. Compared to IDPA, post-stenotic dilation from valve disease is more likely to produce compressive symptoms and right heart enlargement, and may be associated with distinct radiographic and electrocardiographic findings (12).

Pulmonary artery aneurysms (PAAs) are typically defined in the literature as a marked dilatation of the pulmonary artery, most commonly with a diameter exceeding 40 mm (14–16). Importantly, even in patients with IDPA, an aneurysm may develop as part of a pathological continuum, as recognized in recent reports (14). PAAs, in contrast to IDPA, are usually focal and associated with underlying conditions such as pulmonary hypertension, infections, or congenital/acquired heart disease (17). Imaging, particularly CT angiography, is crucial for differentiating these entities and assessing the risk of complications. The distinction between IDPA and PAA is clinically relevant, as aneurysmal transformation may occur over time, and both entities may share overlapping risk factors or etiologies (14–16). In children, additional causes of pulmonary artery dilatation include congenital heart defects with shunt lesions (e.g., atrial or ventricular septal defect, patent ductus arteriosus), vasculitides (e.g., Kawasaki disease), and genetic syndromes with connective tissue involvement (18).

Chest x-ray may reveal a prominent pulmonary artery segment or hilar mass. However, findings are non-specific and must be interpreted in context.

Imaging plays a central role in the diagnosis and monitoring of IDPA. Chest x-ray often provides the first clue, revealing a prominent pulmonary artery segment or hilar mass adjacent to the left mediastinum (Table 1) (1). Echocardiography remains the initial imaging modality of choice in pediatric patients, allowing for assessment of pulmonary artery diameter, cardiac anatomy, and hemodynamics. It is non-invasive, readily available, and useful for both diagnosis and follow-up. However, echocardiography may have limitations in visualizing distal pulmonary arteries and their relationships to other thoracic structures, especially in cases where complex vascular anomalies or airway compression are suspected (19). In these scenarios, CT angiography can provide detailed three-dimensional visualization of the main and branch pulmonary arteries, as well as their anatomical relationships with the trachea, bronchi, and mediastinal structures (20). This comprehensive anatomical overview is particularly valuable for ruling out secondary causes of dilatation and for pre-surgical planning. Cardiac MRI offers the advantage of radiation-free imaging and allows for precise quantification of pulmonary artery size and flow, including assessment of pulmonary regurgitation and stenosis through advanced 4D flow techniques (19). The main limitation in young children is the frequent need for sedation or anesthesia, which can present logistical and safety challenges. Right heart catheterization and pulmonary angiography are now rarely required for diagnosis, but may be indicated in selected cases where non-invasive imaging is inconclusive or when invasive hemodynamic assessment is necessary.

There are currently no established guidelines for the management of IDPA, especially in children. Most patients—particularly those who are asymptomatic and have stable arterial dimensions—are managed conservatively with regular imaging surveillance. Surgical intervention is typically reserved for patients at high risk of rupture, those with symptoms attributable to compression of adjacent structures, or progressive dilatation. Importantly, pediatric intervention thresholds should be based on z-scores and clinical judgment, not adult cut-offs. Cases of giant dilatation in children have been reported without rupture or need for surgery; thus, the risk of rupture appears to be very low in the pediatric population (1).

The initiation of Bosentan and Hydroxyurea in this patient was not specifically for the treatment of IDPA, rather, it was informed by the presence of comorbid hematological abnormalities, including hypersplenism and thrombocytopenia, as well as concerns regarding the potential development of pulmonary vascular disease or hemolytic complications. Bosentan, an endothelin receptor antagonist, is indicated for the management of pulmonary arterial hypertension, while hydroxyurea is utilized in the treatment of select hematologic disorders. In this patient, treatment was initiated as a precaution given the evolving clinical scenario and multidisciplinary consensus, although there was no direct evidence of pulmonary hypertension on hemodynamics. The rationale for splenectomy was management of hypersplenism and refractory cytopenias.