Sarcoidosis, Rheumatoid Arthritis Linked to Silica Dust

Silica dust exposure may trigger sarcoidosis and seropositive rheumatoid arthritis, a new study has shown. The higher the dose of silica the patient is exposed to (> 0.048 mg/m³), the greater the risk.

Currently, there is no clear cause or known trigger for sarcoidosis. Dr Pal Graff and colleagues in Sweden think that the development of sarcoidosis is multifactorial and may stem from environmental exposure combined with genetic predisposition.

An earlier study in Iceland indicated that the incidence of sarcoidosis was much higher in persons exposed to limestone in a quarry than in those not exposed.

The authors of the current study examined a cohort of Swedish iron workers exposed to silica in an effort to determine whether there is a relationship between exposure and sarcoidosis or rheumatoid arthritis.

They presented their findings in a recent BMJ Open article.

The study

Included in this retrospective cohort study were 2187 male foundry workers. Exposure to silica was determined as well as a diagnosis of rheumatoid arthritis or sarcoidosis.

The results

• Silica exposure for workers of indicated job categories varied between 0.0025 mg/m³ and 4.9 mg/m³.

• Silica exposure declined significantly from the 1970s to the 2000s.

• There were 7 cases of sarcoidosis; 4 of the 7 patients with sarcoidosis had the highest silica exposure (standardized incidence ratio [SIR], 3.92; 95% confidence interval [CI], 1.07-10.03).

• There was an increased risk of rheumatoid arthritis in those exposed to silica, with 30 cases (SIR, 1.52; 95% CI, 1.00-2.21).

• There was a significant increase in seropositive rheumatoid arthritis but not seronegative rheumatoid arthritis in those exposed to silica (18 cases; SIR, 1.70; 95% CI=1.01-2.69 versus 12 cases; SIR, 1.41; 95% CI=0.68-2.59).

• There was increased risk of seropositive rheumatoid arthritis in patients with high (> 0.048 mg/m³) silica exposure (SIR, 2.59; 95% CI=1.24-4.76).

Implications for physicians

• Silica exposure may trigger sarcoidosis and granuloma formation.

• Silica exposure may lead to seropositive rheumatoid arthritis.

• Physicians should ask their patients about silica exposure if sarcoidosis or rheumatoid arthritis develops.

• There is increased risk with higher exposures to silica.

• Silica exposure should be avoided in patients who may have a genetic predisposition for sarcoidosis or rheumatoid arthritis.

Disclosures:

Financial support provided by Orebo County.

References:

Vihlborg P, Bryngelsson IL, Andersson L, Graff P. “Risk of sarcoidosis and seropositive rheumatoid arthritis from occupational silica exposure in Swedish iron foundries: a retrospective cohort study.” BMJ Open. 2017;7:e016839. doi: 10.1136/bmjopen-2017-016839.