Response to Dr. Reich's letter: "'Sarcoid-like' granulomatous pulmonary disease in world trade center disaster responders: influence of incidence computation methodology in inferring airborne dust causation": "Sarcoid-like" granulomatous pulmonary disease in World Trade Center disaster responders

Particulate matter granulomas masquerading as sarcoidosis: a diagnostic dilemma

Sarcoidosis is a multiorgan disease with no single etiology. Evidence over the years points to complex interactions between environmental and genetic factors and a hypersensitive immune response to these insults. This brief overview discusses the uncertainty in the diagnosis of sarcoidosis versus other granulomatous diseases masquerading as sarcoidosis. The diagnostic dilemma is highlighted by a brief case review. The development of newer techniques in molecular biology and the identification of a panel of biomarkers in the future with appreciable specificity and sensitivity would help in the process. Future studies to determine receiver operating curves (ROC) using multiple biomarker combinations would help develop robust testing. More in-depth studies are also needed for defining the immunological basis of sarcoidosis because recent studies implicate Th17 cells in addition to the Th1 cell pathway. It is very likely that direct exposure to environmental agents and systemic distribution of these agents can elicit an exaggerated immune response leading to multiorgan granuloma formation mimicking sarcoidosis. A genetically susceptible host may be necessary to complete the granulomatous response to the particulate matter.

Occupational causes of sarcoidosis

PURPOSE OF REVIEW

Sarcoidosis, the multiorgan granulomatous disease of unknown cause, remains mysterious. Several important investigations in the past 2 years add to the accumulating evidence for both occupational and environmental causes of granulomatous inflammation.

RECENT FINDINGS

This review considers the most recent studies that contribute to the hypothesis that sarcoidosis occurs when individuals are exposed to foreign antigens and to inorganic particulates that promote inflammation. Major recent findings, such as those emerging from the study of World Trade Center responders, the study of nanoparticles, and cases of work-associated sarcoidosis, support the probability that occupational, as well as environmental, exposures to inflammatory stimuli trigger sarcoidosis-like illness. Major recent studies of microbially rich indoor environments, including moldy indoor workplaces and mycobacterially contaminated settings, contribute to the evidence that a variety of microbial antigens serve as targets for the hypersensitivity immune response in an inflammatory milieu.

SUMMARY

There is increasing evidence that sarcoidosis can occur in workplace settings in which there is exposure to both foreign antigens and inorganic triggers of inflammation that promote an exuberant granulomatous immune response. It is likely that sarcoidosis has more than one cause.