Introduction
This topic covers the silicatoses, a group of chronic fibrosing pneumoconioses caused by inhaling mineral dusts that contain silicon and oxygen. The main disease is silicosis, caused by crystalline free silica. The other three are asbestosis, talcosis and kaolinosis, which differ in the mineral involved, their pathogenic potential and their clinical course. For the exam, know the aetiology, the forms, the pathogenesis, the imaging pattern, the complications and the expertise criteria for each.
Silicosis: aetiology and risk occupations
Silicosis results from long-term inhalation of respirable crystalline silica (quartz, and less often cristobalite or tridymite). Only particles small enough to reach the alveoli, roughly below 5 µm, are important. The disease depends on the cumulative dose, meaning the concentration multiplied by the duration of exposure.
- Risk occupations: mining (especially hard-rock and gold mining), quarrying, tunnelling and drilling, stone cutting and masonry, sandblasting and abrasive work, foundries, ceramics, glass and enamel production, and construction work involving silica-containing materials.
Clinical forms
- Chronic (simple) silicosis: the most common form, after more than about 10 years of moderate exposure. Often asymptomatic at first, with small nodular opacities on X-ray.
- Accelerated silicosis: after heavy exposure over about 5 to 10 years, with faster progression and earlier complications.
- Acute silicosis (silicoproteinosis): after very massive exposure over weeks to about 5 years. It presents as an alveolar proteinosis-like picture with rapidly progressive dyspnoea, hypoxaemia and a poor prognosis.