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Based on study findings, researchers have proposed a new term for respirable crystalline silica exposure-related granulomatous lung disease: silicosarcoidosis.

Backed by findings from nearly three dozen workers with sarcoidosis who also reported occupational exposure to respirable crystalline silica (RCS), researchers have proposed a new term for the exposure-related granulomatous lung disease: silicosarcoidosis. Their findings were recently published in the American Journal of Industrial Medicine.

“By coining the term silicosarcoidosis, we hope to improve identification and diagnosis of this under-recognized condition,” said lead study author Jeremy Hua, MD, MPH, an occupational pulmonologist and researcher at National Jewish Health, in a news release. “Our work underscores the need for clinicians to consider occupational exposures when evaluating patients with sarcoidosis-like lung disease, especially those in high-risk professions.”

RCS dust, the research team explained, is commonly found in construction, mining, and stone fabrication.

Study Design & Cohort Characteristics

To identify features of the overlap condition, the team assembled a case series of 35 workers from the United States, Israel, and Taiwan. The majority were male (97%), and the average age was 48 years.

The mean duration of occupational RCS exposure among the patients was 21 plus or minus 9 years. Common employment sectors were stone fabrication or masonry (34%), mining (20%), cement/concrete/brick manufacturing or sandblasting (14%), and construction (11%).

Histologic Findings

“We found a range of histologic abnormalities in a multinational case series of workers with silicosarcoidosis that overlap with features of both silicosis and sarcoidosis,” the researchers wrote.

Histology findings indicated granulomas in 86% and lymphocytic inflammation and/or lymphoid aggregates in 94% of patients with evaluable lung tissue. Lung interstitial findings showed silicotic nodules in 39%, mixed-dust macules/nodules in 44%, and birefringent dust in 50%, according to the study.

Quantitative Dust Analysis

A novel quantitative microscopy technique developed by the team to measure birefringent dust density in lung specimens found significantly greater quantitative density in workers with silicosarcoidosis (147 ± 179 particles/mm²) compared with healthy controls (12 ± 9 particles/mm²). However, particulate density in workers with silicosarcoidosis was lower compared with coal miners with silica-related progressive massive fibrosis (623 ± 777 particles/mm²).

Diagnostic Implications

Additionally, the study found significant differences in the frequency of histologic abnormalities in larger biopsy samples compared with standard small lung tissue samples. Smaller tissue samples revealed fewer findings of RCS exposure.

“Small tissue biopsy modalities may be insensitive for diagnosing silicosarcoidosis,” the researchers advised, “and highlight the importance of taking a detailed occupational history with a diagnosis of sarcoidosis.”