Table 2.

Summary of histologic findings on initial biopsy and available explant or postmortem assessments.

Histologic Findings at Diagnosis and Explant or Autopsy
	Diagnostic biopsy				Explant/ Post-mortem
Patient	Alveolar Simplification	Capillary features	Dilated Shunt Veins	Arteriolar Muscularization	Lung development and capillarization
1	Mild and patchy	Most capillaries in a single layer adjacent to epithelium with patchy double-layering	About half of examined BVBs	Moderate	26 months – Normalized RAC, patchy foci with thickened alveolar septa and misaligned veins
2	Mild and patchy	Most capillaries in a single layer adjacent to epithelium with patchy double-layering	About half of examined BVBs	Moderate to severe	4 months – Normalized RAC, rare foci with thickened alveolar septa and patchy misaligned veins
3	Severe	Frequent to nearly uniform remote capillaries and reduced number	Most BVB	Severe	N/A
4	Mild but uniform	Most capillaries in a single layer adjacent to epithelium but decreased in density	Most BVB	Moderate	10 months – Improved alveolarization but abnormal RAC, patchy normal capillaries. Obliteration of arteriolar lumen from intimal expansions and foam cells.

Abbreviations: bronchovascular bundles (BVBs) and radial alveolar count (RAC)