After the aorta, the pulmonary arteries are the most common site of arterial involvement among the pulmonary manifestations in patients with BD[
4]. PAAs associated with BD tend to be multiple, as seen in our patient. The hemoptysis is the commonest symptom of PAA in BD, and one of the leading causes of death[
5]. In the present case there was no hemoptysis. The aneurysms of the pulmonary arteries, with or without thrombosis, are typical manifestation of BD[
6]. Tunacı et al. reported mural thrombotic changes during regression of PAAs[
7]. The underlying pathophysiologic process is inflammation of the
vasa vasorum of the tunica media, which causes destruction of the elastic fibers of the media and dilatation of the vessel lumen. Thickening of the vessel wall is caused by inflammation and infiltration by lymphocytes, plasma cells and neutrophils. Thrombosis of the pulmonary arteries in BD is usually an in situ thrombosis[
2,
8]. Because the main problem is the inflammation of pulmonary arteries, the main stay of treatment should be the anti-inflammatory and immunosuppressive agents in patients with PAA and BD. A combination of cyclophosphamide and methylprednisolone is used most frequently in patients with PAA[
9]. We know that anticoagulant therapy could increase the risk of aneurysmal rupture and anticoagulant drugs might be unnecessary in BD[
5]. Mehta et al. reported a case with in situ thrombosis with BD[
10]. They reported the patient had remained clinically stable with no further episodes of hemoptysis with immunosuppressive treatment including dexamethasone and cyclophosphamide[
10]. However, there was no radiologically demonstrated efficacy of immunosuppressive treatment on in situ thrombosis. The aim of this report has been to demonstrate the effectiveness of immunosuppressive treatment on in situ thrombosis with PAA in a patient with BD. Contrast-enhanced thorax CT revealed the in situ thrombosis on the wall of PAAs. After the immunosuppressive treatment the in situ thrombosis was completely resolved and PAAs were reduced.
In conclusion, inflammation in pulmonary arteries is causing in situ thrombosis and it contributes to the development of PAAs in patients with BD. The anti-inflammatory and immunosuppressive drugs are essential for the treatment of in situ thrombosis and PAAs in patients with BD.