Case of the Month - February

42 year old male with increasing cough and shortness of breath

 Findings:

Left Image: A conventional Chest X-ray suggests multiple pulmonary nodules, especially in the mid and upper zones. The hila are mildy prominent but there is no evidence of mediastinal lymphadenopathy nor of pleural opacity.

Middle Image: A coronal reconstruction from a high-resolution CT scan of the chest. This confirms the multiple small lung nodules measuring up to 5mm diameter. There is no evidence of interstitial thickening, and there is no air trapping or emphysematous change present

Right Image: The arrow demonstrates an enlarged right paratracheal lymph node, which does not contain calcification.

Diagnosis: 

Chronic Silicosis. On questioning the patient, he divulged he had worked "in the mines" for many years.

The differential diagnosis of the appearances shown above include exposure to other inhalational agents such as coal dust, miliary TB, fungal infection and metastatic cancer.

Discussion:

Silicosis was the first occupational lung disease to be characterised. It is caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in forms of nodular lesions in the upper lobes of the lungs.

The presenting symptoms include cough, shortness of breath and cyanosis and can mimic heart failure or infective conditions including tuberculosis.

The diagnosis is usuall based on occupational history and radiological appearances.

Characteristic radiological findings include small parenchymal pulmonary nodules, concentrated in the mid and upper zones. Lymphadenopthy in the hila and mediastinum can also feature, sometimes with characteristic peripheral "egg-shell" calcification.
More severe disease involves coalescence of nodules, coarse pulmonary fibrosis, and emphysema.

Silicosis has been classified into 3 types: simple chronic silicosis (from more than 15 years exposure to low amounts of silica dust); accelerated silicosis (after exposure to larger amounts of silica over 5 - 15 years); acute silicosis (from short-term exposure to very large amounts of silica).

Progressive massive fibrosis can occur in either simple or accelerated silicosis, but is more common in the accelerated form. It is caused by severe scarring and destruction of lung tissue.

Occupations associated with silicosis include:
   Abrasives manufacturing
   Mining
   Quarrying
   Road and building construction
   Sand blasting
   Stone cutting

Complications: Patients with silicosis are at risk for other disorders, including TB, lung cancer, scleroderma and rheumatoid arthritis.