Accelerated silicosis

Definition

Silicosis is a respiratory disease caused by inhalation of silica dust, which leads to inflammation and scarring of the lung tissue.

Three types of silicosis are seen:

• Simple chronic silicosis -- results from long-term exposure (more than 20 years) to low amounts of silica dust. Nodules of chronic inflammation and scarring provoked by the silica dust form in the lungs and chest lymph nodes. This disease may feature breathlessness and may resemble chronic obstructive pulmonary disease (COPD).
• Accelerated silicosis -- occurs after exposure to larger amounts of silica over a shorter period of time (5 - 15 years). Inflammation, scarring, and symptoms progress faster in accelerated silicosis than in simple silicosis.
• Acute silicosis -- results from short-term exposure to very large amounts of silica. The lungs become very inflamed and may fill with fluid, causing severe shortness of breath and low blood oxygen levels.

Progressive massive fibrosis may occur in simple or accelerated silicosis, but is more common in the accelerated form. Progressive massive fibrosis results from severe scarring and leads to obliteration of normal lung structures.

Alternative Names

Causes

Silica is a common, naturally-occurring crystal. It is found in most rock beds and forms dust during mining, quarrying, tunneling, and work with many metal ores. Silica is a main component of sand, so glass workers and sand-blasters also receive heavy exposure to silica.

Risk factors include any work that includes exposure to silica dust. Mining, stone cutting, quarrying, road and building construction, work with abrasives manufacturing, sand blasting and many other occupations and hobbies involve exposure to silica.

Intense exposure to silica may result in disease in a year or less, but it usually takes at least 10 or 15 years of exposure before symptoms develop. Silicosis has become less common since the Occupational Safety and Health Administration (OSHA) instituted regulations requiring the use of protective equipment which limit the amount of silica dust inhaled.

Symptoms

• Chronic cough
• Shortness of breath with exercise, usually in patients who have progressive massive fibrosis

Additional symptoms that may be associated with this disease, especially in acute silicosis:

• Fever
• Cough
• Weight loss
• Severe breathing difficulty

Exams and Tests

Your health care provider will take a careful medical history that includes many questions about your occupations (past and present), your hobbies, and other activities that may have exposed you to excessive silica. A physical exam will also be performed. Diagnostic tests to confirm the diagnosis and exclude other diseases that may appear similar include:

• Chest x-ray
• Pulmonary function tests
• Purified protein derivative (PPD) skin test (for tuberculosis)

Treatment

There is no specific treatment for silicosis. Removal of the source of silica exposure is important to prevent further worsening of the disease. Supportive treatment includes cough suppression medications, bronchodilators, and oxygen if needed. Antibiotics are prescribed for respiratory infections as needed.

Other considerations for treatment include limiting continued exposure to irritants, smoking cessation, and routine tuberculosis

People with silicosis are at high risk for developing tuberculosis (TB). Silica is believed to interfere with the body's immune response to the bacteria that causes TB. Yearly skin testing to check for exposure to TB is recommended. Treatment with anti-TB drugs is recommended for people with a positive skin test. Any change in the appearance of the chest x-ray may indicate TB.

Support Groups

Support groups with others who suffer from silicosis or related diseases may help you understand your disease and adapt to its treatments and other changes in your life that result from it.

Outlook (Prognosis)

The outcome varies and depends upon the extent of damage to the lungs.

Possible Complications

• Increased risk for tuberculosis
• Progressive massive fibrosis

When to Contact a Medical Professional

Call your health care provider if you have an occupational exposure to silica and symptoms develop.

Prevention

If you work in a high-risk occupation or have a high-risk hobby, wear dust masks and do not smoke. Other protection prescribed by OSHA, such as a respirator, may be indicated.

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Noble J. Textbook of Primary Care Medicine. 3rd ed. St. Louis, Mo: Mosby; 2001:694-696