The Shunt of It

Abstract

Pulmonary arteriovenous malformations (PAVMs) are rare and most often identified in patients with hereditary hemorrhagic telangiectasia (HHT). We describe a patient with severe hypoxemia and orthodeoxia with imaging findings consistent with PAVMs. Resected lung pathologic findings confirmed the presence of numerous microscopic vascular abnormalities within the right lower lobe that was consistent with diffuse pulmonary arteriovenous shunts. Family history was negative for HHT but was positive for pulmonary arterial hypertension (PAH) in two second-degree relatives. A vascular malformation gene panel was negative for genes that commonly are associated with HHT but identified a pathogenic variant in the gene encoding bone morphogenetic protein receptor-2 (BMPR2 p.Cys123∗). Pathogenic variants in BMPR2 are a well-known cause of hereditary PAH; there have been several reports to date of patients with PAVMs and PAH. However, this is the first patient to be reported with a pathogenic variant in BMPR2 to have PAVMs in isolation.

Keywords: bone morphogenetic protein receptor-2; pulmonary arterial hypertension; pulmonary arteriovenous malformation; shunt; variant.

Figure 1

Family pedigree. Current patient listed as BMPR-2 variant with the arteriovenous malformations. No additional family members were available for evaluation or genetic testing. AVM = arteriovenous malformation; PAH = pulmonary arterial hypertension.

Figure 2

A and B, Prominence of right lower lobe pulmonary vessels on A, axial and B, coronal slices on CT pulmonary angiogram.

Figure 3

Conventional pulmonary angiogram shows increased peripheral vasculature in the right lower lobe and early draining of enlarged lower lobe pulmonary veins. Findings were concerning for arteriovenous malformations and microvascular shunting.

Figure 4

A and B, Histologic findings of pulmonary vascular abnormalities. A, Microscopic section of the right lower lobe shows multiple engorged, variably dilated thin vessels throughout the lobules (hematoxylin and eosin stain; original magnification, ×40). B, Elastin stain highlights a delicate elastic layer in these vessels, compatible with veins (original magnification, ×200).

Figure 5

Histologic finding of pulmonary vascular abnormalities. Elastin stain shows larger arteries near disorganized smaller veins in periphery of lobules (original magnification, ×100).

Figure 6

Microscopic section of right lower lobe shows focal hypertrophic arteriopathy with markedly thickened pulmonary arteries (hematoxylin and eosin stain; original magnification, ×100).