داء السيليكوز Silicosis

Dr.Ahmad

Silicosis
Definition
Silicosis is a group of lung diseases that develop following the inhalation of crystalline silica dust (SiO2), usually quartz, but sometimes cristobalite or tridymite--other forms of crystalline silica [1-3]. Examples of occupations with exposure to silica include mining (e.g., coal [4], gold), tunneling, stonework, foundry work, sand blasting, and manufacture of ceramics which leads to inflammation and then scarring of the lung tissue.
types of silicosis
Three types of silicosis are seen:
simple chronic silicosis -- which 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 lyumph 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 (4-8 years). Inflmation, 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
Causes, incidence, and risk factors
Silica is a common, naturally occuring crystal. It is found in most rock beds and it forms dusts during mining, quarrying, tunneling, and work with many metal ores. Silica is a principal 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
Symptoms
chroniccough
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
Signs and tests
a careful medical history that includes many questions about occupations (past and present), hobbies, and other activities that may have exposed 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
Radiographic changes
. Opacities are classified and graded by shape, size, and profusion. CT and HRCT scans are more sensitive for early detection of complicated disease [3]. In simple silicosis, nodules up to 1 cm in diameter are more prevalent in the upper than lower lobes. Coalescence to form nodules >1 cm in diameter signifies PMF, a complication of simple chronic or accelerated silicosis. Radiographs of acute silicosis show air space opacities.
Lymph node involvement ± calcification is prominent in silicosis. So-called "eggshell calcification" occurs in 3-6% of miners with silicosis. For diagnosis, peripheral solid or broken calcification up to 2 mm thick must be present in two or more nodes >1 cm in diameter. At least one ring shadow must be complete. "Eggshell calcification" has also been described in sarcoidosis, Hodgkin's disease after radiation, blastomycosis, histoplasmosis, scleroderma, and amyloidosis [6].
Gross features:
Depending on the type and amount of pigmented dust deposited with the silica, the discrete nodules of simple silicosis may be pale (little dust), brownish (iron oxides), or black (coal dust). In complicated disease, nodules enlarge and become confluent, usually centrally in the upper lobes. Confluent lesions greater than 2 cm in diameter histologically or 1 cm in diameter radiographically are considered to represent PMF [5]. Extrathoracic silicotic nodules have been described in lymph nodes, liver, spleen, and bone marrow [7].

The photo shows a slice of lung from a 61-year-old ceramics worker. It shows diffuse pleural fibrosis (upper right), which involves interlobar fissures; and multiple, hard, black silicotic nodules (arrow marks one), which are confluent in the anterior upper lobe and upper portion of the lower lobe. This is an example of PMF.

This chest X-ray shows coal workers pneumoconiosis - stage II. There are diffuse, small (2 to 4 mm each), light areas throughout both lungs. In the right upper lung (seen on the left side of the picture), there is a light area (measuring approximately 2 cm by 4 cm) with poorly defined borders, representing coalescence (merging together) of previously distinct light areas. Diseases which may explain these X-ray findings include simple coal workers pneumoconiosis (CWP) - stage II, silico-tuberculosis, disseminated tuberculosis, metastatic lung cancer, and other diffuse infiltrative pulmonary diseases

This picture shows complicated coal workers pneumoconiosis. There are diffuse, massive light areas that run together in the upper and middle parts of both lungs. These are superimposed on a background of small and poorly distinguishable light areas that are diffuse and located in both lungs. Diseases which may explain these X-ray findings include, but are not limited to: complicated coal workers pneumoconiosis (CWP), silico-tuberculosis, and metastatic lung cancer.

This chest X-ray shows coal workers pneumoconiosis - stage II. There are diffuse, small (2 to 4 mm each), light areas throughout both lungs. In the right upper lung (seen on the left side of the picture), there is a light area (measuring approximately 2 cm by 4 cm) with poorly defined borders, representing coalescence (merging together) of previously distinct light areas. Diseases which may explain these X-ray findings include simple coal workers pneumoconiosis (CWP) - stage II, silico-tuberculosis, disseminated tuberculosis, metastatic lung cancer, and other diffuse infiltrative pulmonary diseases
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 skin testing.
Persons with silicosis are at high risk for developing tuberculosis (TB). Silica is believed to interfere with the body's immune respone to the bacteria that causes TB. Routine, yearly skin testing to check for exposure to TB, is recommended. Treatment with anti-TB drugs is recommended for persons witha postive skin test. Any change in the appearance of the chest X-ray is suspicious for TB.
Prognosis
The outcome varies and depends upon the extent of damage to the lungs.
Complications
increased risk for tuberculosis
progressive massive fibrosis

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