Figure 4.

a, b) Alveolar capillary dysplasia with misalignment of the pulmonary veins. a) Infant aged 2 weeks, ventilated in neonatal intensive care for severe persistent PH who died 3 days after the biopsy. A low power view of the sample shows the poor acinar development and thickened interstitium. Capillaries are not conspicuous in the interstitium. In the centre of the field is a bronchiole. At the 11 o'clock position relative to the airway is a thickened pulmonary artery, and at the 12 o'clock position is a thin-walled blood vessel larger in diameter than the artery that represents a dilated bronchial vein, the so-called misaligned pulmonary vein. In this field no normal pulmonary veins are visible in the oedematous interlobular septa running obliquely at the corners of the field. Haematoxylin and eosin, original magnification 10×. b) A 3-week-old male who collapsed on day 7 of life and required veno-arterial ECMO. This was discontinued, but he had persistent severe pulmonary arterial hypertesnion and episodes of arterial oxygen desaturation. A lung biopsy was obtained but he died 2 days later. The FOX F1 status was unknown. The biopsy showed features of classical alveolar capillary dysplasia. A section was stained with antibody to cytokeratin. The airspace epithelium stains strongly and highlights the poor acinar development and thickened, oedematous interstitium that is characteristic of this condition. MNF116, original magnification 10×. c) Atypical (partial) alveolar capillary dysplasia. Explanted lung from an infant aged 5 months. A lung biopsy obtained at 4 months of age for interstitial lung disease and PH had shown alveolar capillary dysplasia with misalignment of the pulmonary veins. A section from one of the explanted lungs was stained with antibody to CD34 (to demonstrate vascular endothelium). At the upper centre of the field there is a bronchiole and at the right upper and right lower quadrants branches of a thickened, hypertensive pulmonary artery. In the centre of the field there is an anomalous vein. The lung parenchyma shows thickened alveolar septa that contain abundant capillaries. In contrast to classical alveolar capillary dysplasia there is apposition of the capillaries to the airspaces epithelium. CD34, original magnification 10×.