Silicosis is a very strong risk factor for the progression from tuberculous infection to tuberculosis as this study among South African gold miners shows.
The categories denote different degrees of severity of silicosis, category 0 being the least, category 3 the most extensive silicosis. After seven years of follow-up, almost half of these miners had developed tuberculosis. This puts silicosis into close neighborhood with HIV as a risk factor.
No adjustments were made in this study for the presence of tuberculous infection. As it is likely that not all of these miners were infected with M. tuberculosis, the risk is likely to be even larger.
