Desquamative Interstitial Pneumonitis vs Usual Interstitial Pneumonitis

My colleague and collaborator, the late Edgar G. Harrison, Jr., M.D., was of the opinion that “desquamation” was a fundamental phenomenon in the spectrum of usual interstitial pneumonitis. In our report’ on classic interstitial pneumonitis-flbrosis, we found that almost two-thirds of our biopsies revealed this finding. Harrison believed that the designation, “desquamative interstitial pneurnonitis,” should be reserved for those instances when the alveolar cells were rounded, uniform, and monotonous in appearance and were associated with no or a very slight interstitial reaction. This concept adheres to the original description by Liebow and associates.2 In the report by Tubbs and colleagues,3 their criteria for desquamative interstitial pneumonitis are at great variance with those of Liebow et al2 and of Harrison, and the changes described by Tubbs et al are more in keeping with usual interstitialpnemonitis. Hence, I believe that the conclusions of Tubbs et al3 about desquamative interstitial pneumonitis and usual interstitial pneumonitis being phases of the same disease are not justified. The photomicrographs appearing in the report of Bedrossian and colleagues are more in keeping with the appearance of desquamative interstitial pneumonitis. Does all this nit-picking really make any difference? Only in the sense that if terms like desquamative interstitial pneumonitis and usual interstitial pneumonitis are used, care should be taken to follow the criteria as originally proposed. The finding of Bedrossian et al of localized desquamative interstitialpneumonitis suggests that histopathologic findings might not in this instance be a unifying element in describing a pathologic entity. I am of a similar persuasion, and for that reason the concept of classic interstitial pneumonitis-fibrosis was set forth; that is, the pathologic findings make sense only in the context of a consistent clinical and laboratory setting. Until someone discovers specific etiologic agents or pathogenic mechanisms behind the changes designated as desquamative interstitial pneumonitis and usual interstitial pneumonitis, it must be so.