High prevalence of mollusc shell hypersensitivity pneumonitis in nacre factory workers.

Following the discovery of hypersensitivity pneumonitis caused by the inhalation of mollusc shell dust in two workers from a nacre-button factory, the health status of 26 workers employed in sawing mollusc shells was investigated. The evaluation included the administration of two questionnaires and radiological, functional and immunological assessments of all workers at the outset and 1 year later, when hygienic and therapeutic measures had been taken. Six workers, in whom specific inhalation challenge test was positive, were diagnosed with mollusc shell hypersensitivity pneumonitis, thus yielding a prevalence of 23%. Evidence of diffuse lung disease and systemic symptoms was found in these patients. Nonspecific bronchial hyperreactivity was also found more frequently in patients with mollusc shell hypersensitivity pneumonitis. Specific immunoglobulin G (IgG) level and specific skin testing failed to differentiate patients with mollusc shell hypersensitivity pneumonitis from other exposed workers; whereas, nonspecific skin testing, which was impaired in the patients, did differentiate. Bronchoalveolar lavage and transbronchial biopsy performed in patients with mollusc shell hypersensitivity pneumonitis were consistent with the disease. Removal from an environment containing mollusc shell dust was followed by regression of clinical, radiological and functional changes. The clinical picture of the 20 workers who did not present mollusc shell hypersensitivity pneumonitis remained unchanged, but functional decline was observed despite improvement in the environmental conditions of the factory. This report describes the first series of patients with mollusc shell hypersensitivity pneumonitis studied, and underlines the importance of careful follow-up of workers occupationally-exposed to mollusc shell dust.