© 2007 American Thoracic Society
Is Giant Cell Interstitial Pneumonitis Synonymous with Hard Metal Lung Disease?To the Editor:The large case series of hard metal disease described by Moriyami and colleagues in their article provides an important source of clinico-pathologic data pertaining to a rare, but important interstitial lung disease (1). The implications of the authors' reported observations from an immunological perspective were highlighted in the erudite editorial by Nemery and Abraham in the same issue (2). There were, however, important epidemiologic inferences to be drawn from this report that are also worthy of comment. The authors used electron probe microanalysis to assess the elemental content in lung biopsy material from 85 patients with interstitial lung disease "suspected to be of environmental or occupational origin." Although 23 of the 85 biopsies studied (27%) manifest pathologic findings of giant cell interstitial pneumonitis (GIP), the basis for study inclusion (i.e., etiological suspicion of an occupational disease) is not elucidated and may very well have included such histology as one criterion. This would be a reasonable approach, given that GIP has come to be treated as a pathologic finding wholly attributable to hard metal or related cobalt-containing exposures. Indeed, this was the stated rationale for "delisting" GIP as an "idiopathic" pneumonia in the 2002 American Thoracic Society/European Respiratory Society (ATS/ERS) statement on the classification of idiopathic interstitial pneumonias (3). In that light, the further epidemiologic observation of Moriyama and colleagues is all the more intriguing: of the 23 patients with GIP, 2 (8.7%) had no occupational history of exposure (one was a schoolteacher) and no tungsten or cobalt detectable by probe analysis. A recent case report from India of an office sweeper with GIP but no suspect history also raises the question as to whether sporadic cases of this condition occur that cannot be equated with hard metal lung disease (4). There certainly have been cases of GIP in which an occupational history was atypical, but where metals analysis indicated likely occult cobalt exposure (5). Conversely, a thorough metal analysis can be negative, but nonetheless the occupational or environmental history may be highly suspect, as in the case of a 15-year-old with GIP both of whose parents had occupational exposure to hard metal (6). Nemery and Abraham argue cogently that we need to fill in our knowledge gaps about hard metal lung disease (2). Until we do so, it may have been premature to banish GIP from the schema of "idiopathic interstitial pneumonias," as was done in the ATS/ERS statement (3).
University of California, San Francisco, San Francisco, California FOOTNOTES Conflict of Interest Statement: P.D.B. has no financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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