Block 5: Silicosis and Coal Workers’ Pneumoconiosis - The Natural History Of Silicosis And Its Complications.

THE NATURAL HISTORY OF SILICOSIS AND ITS COMPLICATIONS:

• The radiological or pathological appearance of silicotic nodules in the lung is termed Simple Silicosis.
• Once nodules > 1 cm appear this is termed complicated silicosis or Progressive Massive Fibrosis (P.M.F.).

The figure above presents data from a study of SA goldminers that illustrates the natural history of simple silicosis and PMF.

Simple silicosis and PMF are uncommon with less than 10 years of underground dust exposure, suggesting that this is approximately the time required to accumulate a sufficient lung dust burden to manifest silicosis. Silicosis risk and risk of PMF increases with further exposure.

The X-ray and detail above represent a low profusion of simple silicotic nodules.		The X-ray above illustrates a higher profusion of simple, nodular silicosis.

The X-ray on the left is is an example of PMF. The detail shows the typical features of the upper lobe masses (>1 cm) that develop in PMF as the simple nodules aggregate.		Tuberculosis is one of the most important complications of silicosis (also discussed under TB and occupation).

The two X-rays above show typical radiological features of both tuberculosis and simple silicosis.

Acute variants of silicosis:

Acute variants of silicosis also occur, although these are rare:

• Silico-alveolarlipoproteinosis: describes a variant of this condition related to intense silica exposure.
• Accelerated silicosis: describes a variant of silicosis, also related to intense exposure that develops and progresses fatally over a 5-10 year period.

Other silica associated diseases:

• Scleroderma (Progressive Systemic Sclerosis).
• ? Other autoimmune diseases.
• Nephritis / renal disease.
• Lung cancer.