Idiopathic isolated pulmonary artery aneurysm: a case report

Abstract

Background

Pulmonary artery aneurysms (PAAs) are rare vascular anomalies, most commonly associated with pulmonary hypertension, congenital heart disease, vasculitis, or infection. Idiopathic PAAs, lacking an identifiable underlying cause, are exceptionally rare and often discovered incidentally. This case illustrates the diagnostic approach and rationale for conservative management of idiopathic PAAs in the absence of high-risk features.

Case Summary

We describe a 70-year-old female with a history of asthma, obstructive sleep apnoea, and transient ischaemic attack, in whom a PAA was incidentally discovered following imaging for respiratory complaints. Contrast-enhanced computed tomography (CT) revealed a fusiform aneurysm of the left lower lobe pulmonary artery, with a maximum axial diameter of 4.6 cm, located just distal to the origin of the lower lobe branch from which also the lingula artery arises. Retrospective comparison with a chest radiograph from 10 years earlier confirmed interval growth. There were no clinical or imaging features suggestive of pulmonary hypertension, congenital shunts, or significant valvular disease, nor any clinical or biochemical evidence of infection, connective tissue disease, or vasculitis. Multidisciplinary evaluation supported the diagnosis of an idiopathic and acquired pulmonary aneurysm. A conservative approach with follow-up CT imaging at 6 months, which demonstrated stability of aneurysm size and morphology, was chosen.

Discussion

This case underscores the importance of recognizing rare vascular anomalies in patients with non-specific respiratory symptoms. In the absence of an identifiable underlying pathology, an idiopathic cause should be considered. Conservative management may be appropriate in selected cases lacking high-risk features, though long-term outcomes remain uncertain.

Learning points.

• Idiopathic pulmonary artery aneurysms can rarely involve distal segmental branches, requiring comprehensive imaging to exclude secondary causes and define morphology.

• Conservative management with serial imaging may be appropriate in asymptomatic, haemodynamically stable cases without high-risk features.

Introduction

Pulmonary artery aneurysms (PAAs) are rare vascular abnormalities, with an estimated prevalence of less than 1 in 14 000 in autopsy series.¹ They typically occur secondary to a broad spectrum of conditions, including congenital heart disease (particularly patent ductus arteriosus), connective tissue disorders such as Marfan syndrome, pulmonary hypertension, vasculitis (e.g. Behçet’s disease), infections (e.g. tuberculosis), or trauma.^2,3 In the absence of an identifiable underlying cause, the aneurysm is classified as idiopathic, a diagnosis of exclusion.⁴

Although many PAAs remain asymptomatic and are detected incidentally, they carry a risk of life-threatening complications such as rupture, thrombosis, or compression of adjacent structures.⁴ Guidelines for management are limited, particularly in idiopathic and isolated cases. We report a rare case of a distally located idiopathic PAA, highlighting the diagnostic challenges and the clinical reasoning behind a conservative management strategy in the absence of established guidelines.

Summary figure

Contrast enhanced CT demonstrates a fusiform aneurysm dilatation of the left lower lobe pulmonary artery, with a maximum axial diameter of 4.6 cm, arising distal to the lower lobe.

Case presentation

A 70-year-old woman with a history of asthma, obstructive sleep apnoea, and a transient ischaemic attack presented to her general practitioner with mild upper respiratory symptoms. She reported no cardiopulmonary complaints such as chest pain, haemoptysis, or syncope. A chest radiograph revealed an abnormal contour near the left pulmonary hilum, prompting further evaluation with a contrast-enhanced CT scan (Figure 1).

Figure 1.

Chest radiography. (A) Chest radiograph obtained 10 years earlier showing a subtle abnormal contour near the left pulmonary hilum. (B) Recent chest radiograph demonstrating clear interval growth of the lesion.

CT imaging demonstrated a fusiform aneurysmal dilatation of the left lower lobe pulmonary artery, with a maximum axial diameter of 4.6 cm, arising just distal to the origin of the lower lobe branch, from which the lingula artery also arises (a known anatomical variation).⁵ Retrospective comparison with a chest radiograph obtained 10 years earlier confirmed interval growth. No thrombus, dissection, or compression of adjacent structures were observed (Summary figure).

The patient was referred to cardiology for further assessment. There was no family history of aneurysms or connective tissue disorders. Physical examination revealed no features suggestive of connective tissue disease, including absence of a Marfanoid habitus, negative wrist and thumb sign, and no joint hypermobility. There were no clinical signs of systemic vasculitis or infection, such as fever, weight loss, or peripheral stigmata.

Transthoracic echocardiography showed normal right ventricular size and function (see Supplementary material online, Video S1), a non-dilated ascending aorta, and no significant valvular disease. Estimated pulmonary artery systolic pressure was 26 mmHg, with a central venous pressure of 3 mmHg (Figure 2). No intracardiac shunts, abnormal flow across the pulmonary valve, or indirect echocardiographic signs of a patent ductus arteriosus or arteriovenous fistula were identified. A soft systolic murmur was noted, likely due to altered pulmonary flow dynamics. Laboratory tests showed no significant elevation of inflammatory markers.

Figure 2.

Transthoracic echocardiography with agitated saline improved tricuspid regurgitation assessment and pulmonary pressure estimation, yielding a pulmonary artery systolic pressure of 18 mmHg without contrast and 26 mmHg with contrast.

The case was reviewed by a multidisciplinary team, including pulmonology, radiology, and thoracic surgery. The aneurysm was characterized as fusiform and non-inflammatory, with no radiological features suggestive of infection (including perivascular inflammation, gas formation, or lymphadenopathy), and no alternative underlying aetiology could be identified despite comprehensive clinical, laboratory, and imaging evaluation. In the absence of an identifiable underlying cause, the aneurysm was classified as idiopathic and likely acquired. After discussion with the patient, a conservative management strategy was proposed, consisting of follow-up CT imaging at 6 months, with further follow-up intervals to be determined based on stability. The 6-month follow-up CT scan demonstrated no change in aneurysm diameter or morphology, supporting the decision to continue conservative surveillance with repeat CT imaging after 1 year.

Discussion

This case illustrates the diagnostic and therapeutic uncertainty that can arise in incidentally discovered PAAs without an evident underlying cause, even after systematic exclusion of common secondary aetiologies.

The aneurysm’s fusiform morphology and its distal location in the left lower lobe pulmonary artery are unusual, as most idiopathic PAAs involve the main pulmonary artery or proximal branches.^3,4,6 This distal, segmental localization supports a chronic, structurally evolved process rather than an acute or inflammatory one, and the absence of pulmonary hypertension further supports a non-haemodynamic mechanism in this case.

Although idiopathic PAAs are rare and poorly characterized, intrinsic weakness of the arterial wall, possibly related to cystic medial degeneration, has been proposed as a mechanism that allows progressive dilation even in the absence of pulmonary hypertension or increased flow.⁷ In this patient, the documented interval growth and the absence of structural, infectious, inflammatory, or haemodynamic abnormalities make an idiopathic aetiology the most plausible explanation.

Rupture and dissection remain the most feared complications of PAAs, with reported mortality rates up to 50%–100%.⁸ However, idiopathic low-pressure PAAs have a more benign natural history compared with those associated with pulmonary hypertension or congenital defects, with rupture or dissection being rare in the absence of high-pressure or rapid growth.^9,10 The pulmonary circulation is a low-pressure system, and the pulmonary artery wall contains less elastic tissue and a thinner media than the aorta, which may partly explain differences in aneurysm progression and rupture thresholds between these vessels, although direct comparative studies are limited.^11,12

There is no consensus on the management of isolated idiopathic PAAs, largely due to their rarity and the absence of dedicated prospective data. Although size- and pressure-based risk thresholds have been proposed,¹¹ these are derived from heterogeneous PAA populations rather than idiopathic cases, leaving the true rupture risk in this subgroup uncertain. In clinical practice, treatment decisions are largely based on expert opinion and small case series.^4,10,11 Surgical repair is generally recommended for symptomatic patients, aneurysms exceeding 5.5–6.0 cm, those demonstrating interval growth of ≥5 mm within 6 months, thrombus formation, or compression of adjacent structures.^4,7,11 In contrast, conservative management with close imaging surveillance is often accepted for asymptomatic, haemodynamically stable idiopathic PAAs, provided there are no high-risk features.^9,10

In our case, the aneurysm measured 4.6 cm, remained stable at 6-month CT follow-up, and had shown slow progression over approximately 10 years. The patient was asymptomatic, with normal pulmonary pressures and no thrombus or compression. These features, combined with the absence of right ventricular dysfunction or pulmonary regurgitation, supported a conservative approach with continued surveillance.^9,10 Moreover, the very distal location of the aneurysm would make surgical repair technically challenging, potentially requiring lobectomy or pulmonary artery sleeve resection after heparinization by temporarily clamping the artery proximal and distal to the lesion. This further favours a conservative strategy in such an asymptomatic, haemodynamically stable patient.^13–15

Taken together, this case illustrates how structured diagnostic workup and multidisciplinary evaluation can support conservative management of an idiopathic PAA in the absence of high-risk features. At the same time, it highlights the limited evidence base and the need for more structured, preferably prospective or registry-based data to guide management of this rare entity.

Patient perspective

The patient was primarily concerned about the implications of the aneurysm and expressed anxiety regarding its potential consequences. She was particularly worried about the risk of rupture and whether surgical treatment would be necessary. After detailed explanation and reassurance, she appreciated the structured follow-up plan and felt more at ease knowing the condition would be monitored closely.

Lead author biography

Dr. Lilaf Abdulmajid obtained her medical degree from the University of Antwerp, Belgium. She is currently training in cardiology at the University Hospital Antwerp and is completing her residency at Jessa Hospital in Hasselt, Belgium. Her clinical interests include heart failure and cardiac imaging.

Supplementary material

Supplementary material is available at European Heart Journals – Case Reports online.

Author contributions

Lilaf Abdulmajid (Writing—review & editing [lead]), Domien Jans (Writing—review & editing [supporting]), Karel Smeyers (Writing—review & editing [supporting]), and Paul Dendale (Supervision [lead])

Consent: The authors confirm that written consent for submission and publication of this case report, including images and associated text, has been obtained from the patient, in line with COPE guidance.

Funding

No specific funding was received for this work.

Data availability

Data sharing is not applicable to this article as no new data were created or analyzed in this case report.