Reaching a peak at days 4 to 5, hyaline membranes
are composed of plasma proteins and cellular debris gathered into dense, glassy eosinophilic membranes found along alveolar septa with accentuation in alveolar ducts.
Diffuse alveolar damage (DAD) is a pathology term that describes the presence of alveolar fibrin, hyaline membranes
and reactive epithelial cells within alveoli, with varied stages of inflammation.
RBCs and leukocyte infiltrates were seen in 13 and alveolar hyaline membranes
in 9 cases.
The most common histopathologic finding was diffuse alveolar damage comprising intraalveolar edema, hyaline membranes
, fibrin, and hemorrhage.
Microscopic findings have included interstitial infiltrates of mononuclear cells in the alveolar septa, congestion, septal and alveolar edema with or without mononuclear cell exudate, focal hyaline membranes
, and occasional alveolar hemorrhage.
Radiologically, the early exudative phase shows bilateral and patchy ground-glass densities, corresponding to interstitial edema and hyaline membranes
5 (8-27) Cardiac massage in first 48 h 6 (50) Endotracheal intubation in first 48 h 11 (92) Respiratory distress syndrome 11 (92) Hyaline membranes
disease 9 (75) Bradypneic syndrome 7 (58) Bronchopulmonary dysplasia 8 (67) Amniotic fluid aspiration 1 (8) Invasive mechanical ventilation, d, median (range) 12 (2-50) Endotracheal intubation during hospital stay 12 (100) Infectious complications Lung infection 5 (42) Other systemic infection 7 (58) Other complications Intraventricular hemorrhage 4 (33) Persistent artery canal 7 (58) Necrotizing enterocolitis 2 (17) Congenital malformations 1 (8) Hospitalization Stay in neonatology ward, d, [section] median (range) 113.
The pathologic stages of ALI/ARDS or diffuse alveolar damage can be divided into 3 subsequent and somewhat overlapping phases: (1) exudative phase, characterized by neutrophilic infiltrate, hemorrhage, and the accumulation of a protein-rich pulmonary edema; (2) fibroproliferative phase, including chronic inflammation, early fibrosis, resorption of hyaline membranes
, and neovascularization; and (3) recovery phase, seen in surviving patients.
Pulmonary congestion with edema was note& but hyaline membranes
had not formed (Figure A).
7) Most pathologists are well familiar with the histologic findings of DAD from the autopsy suite, especially the acute form with hyaline membranes
, although the organizing phase may not be as readily recognized.
may be seen at this point and may reach a peak 4 to 5 days after the initial insult.
On autopsy, HPS is marked by a constellation of findings, including large pleural effusions, severe fibrinous pulmonary edema with hyaline membranes
, and an immunoblastic proliferation involving the reticuloendothelial system.