What is Sarcoidosis

Sarcoidosis is a disease of unknown cause involving the formation of nodules of chronically inflamed tissue in many sites throughout the body. Sarcoidosis usually affects the lungs and nervous system, but can cause disease in other organs too.
Sarcoidosis usually affects young and middle-aged adults. Sarcoidosis may rarely be fatal.

Statistics on Sarcoidosis

Sarcoidosis is relatively commonly detected as an incidental finding on chest x-ray – that is, the patient may have had no symptoms before the diagnosis.
Sarcoidosis usually presents in adults younger than 40 years, most frequently between 20-30 years of age. Women are more likely to develop sarcoidosis than men. Systemic sarcoidosis (disease involving the whole body) affects 1-50 per 100 000 people. Neurosarcoidosis (disease affecting the brain or nervous system) affects 5 people per 100 000.
There is a large geographical variation in the incidence of sarcoidosis: it is common in the USA but rare in Japan and South-East Asia. Lifetime risk is highest for people of American-African origin.

Risk Factors for Sarcoidosis

The cause of sarcoidosis is not well understood, although multiple theories exist.
Currently, sarcoidosis is thought to result from a combination of genetic, infectious and environmental factors that trigger an immune response causing the formation of granulomas (lumps of abnormal inflammatory tissue).
Though cases of sarcoidosis seem to run in families, no gene has been identified as responsible. Other factors, such as infection with certain bacteria, fungi, or viruses, have also been suggested.

Progression of Sarcoidosis

Sarcoidosis is a condition that can affect many different organ systems including:

  • Lungs (87%)

 

  • Lymph nodes (28%)
  • Skin (18%)
  • Eyes (15%)
  • Central nervous system (5-16%)
  • Peripheral nervous system (6-18%)The course of the disease is difficult to predict. The majority of cases spontaneously improve or resolve over 2-3 years. Even when sarcoidosis lasts longer, most patients can go about their lives as usual. Sarcoidosis is not a cancer. It is not contagious, and your friends and family will not catch it from you. Although it can occur in families, there is no evidence that sarcoidosis is passed from parents to children.

    How is Sarcoidosis Diagnosed?

    The diagnosis of sarcoidosis is made on the basis of examination findings and further tests.
    These include:

    • chest x-rays, which may show distinctive lung changes that characterise sarcoid;
  • blood tests, which may show mild anaemia, raised calcium levels, or raised markers of inflammation;
  • CT; and
  • lung function tests to determine amount of lung damage.Other tests may include: lumbar puncture, muscle biopsy, nerve conduction studies and a Kveim test (a special test for sarcoid).

    Prognosis of Sarcoidosis

    It is difficult to predict how sarcoidosis will progress in an individual patient. Factors such as the ethnicity of the patient, and the extent of lung disease on chest x-ray may provide some guidance. However, even extensive lung involvement has been known to disappear spontaneously, and sometimes no progression of the disease occurs for many years.
    A number of patients will develop complications due to lung, eye or other organ damage. In general, only 3% of patients will die from their sarcoidosis. The most common cause of death is lung failure.

    How is Sarcoidosis Treated?

    Patients with sarcoidosis who do not have symptoms don’t require treatment, even if x-rays or blood tests are abnormal. This is because the side effects of the treatments used may be considerable, and hence are only used to treat disease with symptoms.
    Corticosteroid medications such as prednisolone are the current treatment of choice, as they have been shown to improve symptoms and reduce lung disease as seen on a chest x-ray. These may be used for all manifestations of sarcoidosis – lung, heart, liver, nervous system, skin or eye disease. They may be taken orally, given intravenously in severe disease, or inhaled to relieve breathlessness. Corticosteroids have a number of side effects, such as weight gain, skin thinning, euphoria, high blood sugar, osteoporosis and increased rate of infections.
    For a small number of patients corticosteroid medications will not be enough to control their symptoms. In these cases, immunosuppressant drugs, such as those used to treat cancer may be more effective. Surgery or radiotherapy may be needed to treat sarcoid affecting the brain.
    Relapse of sarcoidosis is common once treatment has ended. For this reason, it is necessary to monitor patients even after their symptoms have improved.

    Sarcoidosis References

    1. Cotran, Kumar, Collins. Robbins Pathological Basis of Disease, 6th ed. WB Saunders, United States of America (1999).
    2. Hankey G., Wardlaw J. Clinical Neurology. Demos Medical Publishing, United Kingdom, 2002.
    3. Kumar and Clark. Clinical Medicine, 5th ed. WB Saunders, Toronto (2002).
    4. The Merck Manual of Diagnosis and Therapy: Sarcoidosis.
      [available online @ http://www.merck.com/]
    5. Talley NJ, O’Connor S. Clinical examination. Third Ed. MacClennan & Petty, 1996. p126
    6. Wu, Rashchovsky. Sarcoidosis. Am F Phys 2004.
      [available online @ http://www.aafp.org/afp/20040715/312.html]