Background
Aside from thoracic trauma and rupture of the great vessels, spontaneous hemomediastinum is an uncommon and often life threatening event. Neurofibromatosis 1 (NF1, von Recklinghausen’s disease) is a rare cause of effusion of blood into the mediastinum. NF1 is the most common of at least eight clinical phenotypes of neurofibromatosis occurring in about 1 out of 2 000~5 000 individuals (Hung et al., 2012; Rasmussen and Friedman, 2000). It is an autosomal dominant disorder which arises from mutation of the gene at chromosome 17q11.2, which is responsible for neurofibromin production (Gottfried et al., 2006). This leads to cell proliferation and inhibited apoptosis throughout the body, especially in the nervous system (Cawthon et al., 1990). Vascular lesions associated with NF1are infrequent, but can be fatal, and are characterized by stenosis, occlusion, aneurysms, pseudoaneurysms and rupture or fistula formation in small, medium, and large arteries (Seow et al., 2007). The intercostal, subclavian and bronchial arteries are the commonest vessels involved in mediastinal hematomas (Miyazaki et al., 2011). Only one case of internal mammary artery involvement has been documented so far (Conlon et al., 2007). Here, we describe a case of spontaneous mediastinal hemorrhage as a result of pseudoaneurysmal rupture of the right internal mammary artery.

Case Summary
A 59 years old female with a past medical history of neurofibromatosis, malignant peripheral nerve sheath tumor on chemotherapy, right sided breast carcinoma status post resection and radiation was admitted for acute respiratory failure secondary to health care associated pneumonia. She was intubated and cared for in the intensive care unit.

During the admission, she was suddenly found to be tachycardiac with decreased right sided breath sounds and a 3 mg/dl drop in hemoglobin. A chest x-ray showed a widened mediastinum. Computed tomography (CT) revealed a 9.1 cm by 6.1 cm right paramediastinal hematoma and a pseudo-aneurysm arising from the right internal mammary artery with a 5cm hematoma just inferior to it. She received four units of packed red blood cells. In line with her health care proxy’s decision, surgical intervention was withheld and she was conservatively managed for two weeks. She gradually improved, was discharged with a stable hemoglobin of 10.2 g/dl. A six month follow up was unremarkable (Figure 1; Figure 2; Figure 3).
 

Figure 1 Scout image showing right mediastinal mass

Figure 2 Pseudoaneurysm

Figure 3 Hematoma

Discussion
The incidence of vascular lesions in NF1 is reported as 3.6% (Rasmussen et al., 2001). Neurofibromin is expressed in blood vessel endothelial and smooth muscle cells and NF1 vasculopathy may result from an alteration of neurofibromin function in these cells (Hamilton and Friedman, 2001). Lessened NF1 gene function, especially in response to arterial injury, leads to intimal thickening and decreased luminal size (Lasater et al., 2010). As a result of the fragility and dysplastic nature of the arteries, spontaneous rupture may occur over time. Another pathogenic mechanism that has been endorsed is direct invasion of vessels by adjacent neurofibromata, neurofibromasarcomas and schwannomas (Chew et al., 2001).

Bleeding from arterial aneurysms and pseudoaneurysms can be lethal. When such situations are encountered, both surgical and medical treatment options are available. In hemodynamically unstable situations, emergent andaggressive surgical intervention is recommended. Whereas, if the patient is hemodynamically stable, a more conservative approach with endovascular embolization or nonoperative management may suffice (Pezzetta et al., 2003). Thevessels associated with NF-1 are friable making surgical control a difficult task. Therefore, whenever a patient is reasonably stable, urgent angiography with percutaneous embolization may be employed and thus far this approach has shown a superior outcome to surgical intervention (Teitelbaum et al., 1998; Kipfer et al., 2001; Morello et al., 2001; Dominguez et al., 2002).

Radiation is said to have deleterious effects on the vascular endothelium such as fibrinoid necrosis and subendothelial edema in arteries (Hasleton et al., 1985). Therefore, it is pertinent to mention radiation was used to treat our patient for breast cancer. It is not clear if there was an association between radiation and the development of an internal mammary artery aneurysm in this patient.

A high index of suspicion is required to abort the vascular complications of NF1. The possibility of aneurysmal rupture in a patient with neurofibromatosis1 presenting with an acute hemoglobin drop should be entertained as one of the differential diagnoses. Surveillance with CT angiography in patients with NF1 and other conditions that increase the risk of vasculopathy is recommended.

Authors’ contribution
All authors contributed significantly in drafting the manuscript. The three authors read and approved the final manuscript. 

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