Haemoptysis in an immunocompromised patient with angioinvasive pulmonary aspergillosis and associated mycotic aneurysm of left subclavian artery

Clinical History

Case of acute lymphoblastic leukaemia on chemotherapy. The patient had fever with low neutrophil count (300/cumm). CT chest performed and patient managed conservatively with antimicrobial therapy. TLC improved to 12,400/cu.mm. Presented after 1 month with 3-4 episodes of haemoptysis over 2 days. Managed conservatively, underwent imaging & bronchoscopy for diagnosis of cause of haemoptysis.

Imaging Findings

Initial CECT chest (neutrophil count -300/cumm) showed nodular lesions with parenchymal infiltrates in both lungs befitting the ‘CT halo sign’. Next CECT chest 1 month later revealed nodular and cavitating lesions in both lungs. A few of the cavitating lesions showed heterogeneously hypodense contents with 'air crescent sign’. On shifting the patient’s position to right lateral decubitus, the air crescent showed change in position of fungal ball. The left subclavian artery just above its origin from the arch was found encased by a left upper lobe mass with evidence of pseudoaneurysm formation. CECT angiography for confirmation revealed pseudoaneurysm arising from left subclavian artery measuring 3.1cm × 2.8 cm × 3.0 cm arising about 3 cm distal to the subclavian artery origin from the arch of aorta and encased by the cavitating lesion in left upper lobe. KOH preparation from bronchoscopic lavage performed next day revealed fungal hyphae confirming the diagnosis of angioinvasive aspergillosis.

Discussion

Angioinvasive aspergillosis involves fungal invasion and occlusion of small and medium sized pulmonary arteries [1] causing pulmonary haemorrhage, arterial thrombosis, and infarction [2]. Mycotic aneurysms develop via embolism of the vasa-vasorum, direct wall invasion and vessel erosion from an adjacent lung lesion [3].
Angioinvasive aspergillosis occurs almost exclusively in immunocompromised and severly neutropaenic patients. Immunosuppresion can cause functional neutropaenia and may also affect patients with normal neutrophil count [1]. A delayed or improperly treated infection has a 65%–90% mortality rate necessitating early diagnosis [4]. While sputum cultures for aspergillus are positive in only 10% patients [5], more invasive diagnostic approaches, including bronchoscopy with transbronchial biopsy, percutaneous aspiration biopsy are usually met with relative contraindications like thrombocytopaenia or respiratory compromise. Hence, imaging findings that suggest the diagnosis of invasive pulmonary aspergillosis are important.

In early stages of infection (neutropaenic period), CT is more sensitive and specific than chest radiographs [6]. CT may demonstrate areas of ground-glass attenuation surrounding nodular opacities which represents pulmonary haemorrhage -"CT halo sign". In the appropriate clinical setting, it is highly specific for invasive aspergillosis and should lead to prompt institution of antifungal therapy.

The air crescent sign in angioinvasive aspergillosis is caused by necrotic lung tissue (pulmonary sequestra) mixed with hyphae surrounded by a thin rim of air. This is usually seen with resolution of neutropaenia and has limited diagnostic utility. The air crescent sign in patients with aspergilloma involves fungal ball formation in a pre-existing (usually tubercular) lung cavity which should not be confused with that in patients with angioinvasive aspergillosis.

Cases of mycotic aneurysm caused by aspergillosis are rare, even more so as regards involvement of subclavian artery [3, 7]. Diagnosis and pretreatment workup of mycotic aneurysms has been simplified by advent of multidetector CT angiography which can non-invasively localise the involved arterial branch. This depicts underlying lung parenchymal and mediastinal involvement with high sensitivity, providing a detailed vascular road map for the treating interventional radiologist or surgeon.
Treatment options employed among cases mentioned in literature include surgical application of aneurysm with partial lobectomy [7] and endovascular repair using stent graft [8] as an alternative. The choice in any particular case will depend on patient’s condition and available expertise.

In immunocompromised patients with haemoptysis and multiple lung shadows, mycotic aneurysm formation should be actively look for and treated early to control haemoptysis and reduce associated high mortality and morbidity. This patient was referred for further interventional management at an equipped centre.

Differential Diagnosis List

Final Diagnosis

Immunodeficiency induced angioinvasive aspergillosis causing subclavian artery mycotic aneurysm post-chemotherapy.

URL:	https://www.eurorad.org/case/10069
DOI:	10.1594/EURORAD/CASE.10069
ISSN:	1563-4086