A self referred group of four workers from a factory producing scouring powder with a high silica content showed a surprisingly high number of features compatible with a connective tissue disease. Further subjects working at the same factory were subsequently studied to evaluate the relation between this exposure and the development of autoimmune processes.
A total of 50 subjects (44 women, six men; mean (SD) age 43.7 (5.5) years; mean duration of employment 6.1 years) underwent a prospective study including clinical history and physical examination, an immunobiological study, HLA typing, radiological and functional oesophageal and respiratory examination, ophthalmological examination, and isotopic testing of salivary glands.
Symptoms of a systemic illness were present in 32 (64%) subjects: six with Sjögren's syndrome; five with the criteria for systemic sclerosis; three with systemic lupus erythematosus (SLE); five with an 'overlap syndrome'; and 13 with undifferentiated findings not meeting the criteria for a defined disease. Antinuclear antibodies were present in 36 (72%) subjects; four had antibodies to native DNA, including two subjects with SLE, one with systemic sclerosis associated with secondary Sjögren's syndrome, and one with overlap syndrome. Anticentromere antibodies were not detected. The frequency of HLA-DR3 was increased in the clinically affected subjects, but did not reach statistical significance.
This descriptive study emphasises the high probability of workers occupationally exposed to silica developing a multiple spectrum of clinical and serological autoimmune manifestations.