Diffuse Alveolar Damage: Also referred to as DAD is a configuration that is seen histologically in disease of the lung. It is seen in “acute interstitial pneumonia” or AIP, “acute respiratory distress syndrome” or ARDS; as well as “transfusion related acute lung injury” or TRALI.

It is a quite common finding in biopsy. Thru histology, DAD goes thru numerous stages: exudative phase which is similar to pulmonary edema where the alveoli become flooded with transudate; hyaline membrane creation where the membranes are fibrous structures laid down so as to stop any oxygen from being absorbed via the alveoli that are damaged; as well as the third phase that is call the organized phase.