Although generally assumed to be associated with the specific pathologic pattern known as diffuse alveolar damage (DAD), ARDS is a syndrome rather than a specific diagnosis. In some cases ARDS results from a specific underlying inflammatory lung disease. Infectious and non-infectious causes have been cited.
Non-infectious underlying diseases mimicking ARDS were reviewed several years ago in this Chest article. Acute exacerbations of ILD in connective tissue disease, pulmonary vasculitis, acute eosinophilic pneumonia, anti-GBM disease, diffuse alveolar hemorrhage, acute BOOP, and acute interstitial pneumonia (AKA Hammon Rich syndrome) were cited. These disorders require an aggressive diagnostic effort, are generally treated with steroids with or without a second immunosuppressive agent and with specific treatment may have a better survival that ARDS across the board. (This use of steroids is to be distinguished from the controversial uses of steroids now being discussed for patients with ordinary ARDS and severe pneumonia).
Now a new paper in Chest presents an autopsy series of ARDS patients. Disturbingly only half the patients had DAD with infectious causes noted in the remainder including pneumonia, invasive aspergillosis and disseminated tuberculosis.
Clearly some patients with ARDS should be considered for aggressive diagnostic work ups including invasive evaluation, but which ones? Be suspicious of those who present without circumstances suggesting an underlying cause (trauma, sepsis, etc).
Finally, don’t forget that blastomycosis occasionally presents as ARDS even in otherwise normal hosts.