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134 Chapter 3: Respiratory system

Table 3.20 Chest X-ray appearance in pneumoconiosis this is due to impairment of local defences, as a result
of the accumulation of silica in macrophages. Increased
Pattern Chest X-ray appearance
risk of lung cancer.
Simple
pneumoconiosis
Stage 1 Small round opacities are present Investigations
but few in number Chest X-ray in the early stages shows reticular/nodular
Stage 2 Small round opacities numerous shadowing.Withprogressionthereareradiologicalsigns
but normal lung visible of massive fibrosis (destruction and lesions in the upper
Stage 3 Small round opacities, normal zones), and thin streaks of calcification around the hilar
lung totally obscured
Progressive massive Round fibrotic masses, several cm nodes (‘eggshell calcification’).
fibrosis in diameter, in upper lobes
Management
There is no specific treatment, primary prevention
Silicosis through education and exposure prevention remains the
only effective stratergy.
Definition
Arare lung pathology resulting from the inhalation of
silica dust (quartz).
Respiratory oncology
Aetiology
This condition is mainly seen in workers in slate mines Bronchial carcinoma
and granite quarries, metal foundries, stone masonry
and tunnelling. Definition
A malignant tumour of the bronchial (most common)
Pathophysiology or rarely alveolar epithelium.
The pathogenesis is thought to be a toxic effect on
macrophages, which stimulate cytokine generation, pre- Incidence
cipitating fibrogenesis. Short heavy doses produce acute Bronchialcarcinomaisthemostcommonmalignancyof
silicosiswithpulmonaryoedemaandalveolarexudation. the Western World: 40,000 deaths per year in the United
Prolonged exposure produces multiple fibrous nodules, Kingdom, more than 1 million deaths worldwide.
which may expand causing extensive destruction of It is the leading cause of death from cancer in men
lung tissue and the development of progressive massive and in women under the age of 65, it has now exceeded
fibrosis. breast cancer as the leading cause of death from cancer.

Clinical features
Age
In the early stages there may be no symptoms. The first
Peak age 40–70 years.
symptomisusuallybreathlessnessonexertionandapro-
ductive cough may follow. Progression leads to respira-
tory failure. Sex
3M : 1F, but rising in females.
Microscopy
The nodules in silicosis are made up of collagen and Geography
contain silica particles which can be identified using po- Follows patterns of smoking, independent of this it is
larised light. also higher in urban areas.

Complications Aetiology
The development of tuberculosis is a common compli- Around 80–90% of cases occur in smokers (see Table
cation of silicosis (silicotuberculosis). It is thought that 3.21).