Sarcoidosis is a disease that can affect various parts of the body but most commonly the lungs and lymph nodes. The disease causes extensive lung inflammation, which leads to a persistent cough, feeling short of breath, extreme tiredness and people affected often lose weight. Fortunately, sarcoidosis is rarely fatal and usually clears up with two years of low-dose steroid treatment.
What causes sarcoidosis?
Sarcoidosis is caused by an overreaction of the immune system. When the immune system fights off an invasion by viruses or bacteria, white blood cells accumulate at the site of the infection. When the infection has been overcome, the white cells usually just disperse.
In cases of sarcoidosis, the white cells remain in a high state of alert and form dense masses known as granulomas. The name sarcoidosis comes from the Greek sarco, meaning flesh-like processes, which describes the appearance of the granulomas in tissue.
The granulomas that form may cause inflammation, tissue damage and scarring wherever they occur. In the lungs, sarcoidosis causes lung inflammation and eventually lung fibrosis in which normal lung tissue is replaced by thickened scar tissue that is useless for gas exchange.
The impact of sarcoidosis
Sarcoidosis affects different people in different ways and may be mild to very severe. Some cases of sarcoidosis produce no symptoms at all and go undetected for years. The condition may even clear up; leaving no evidence that there was ever a problem. At the other end of the scale, sarcoidosis can cause permanent scarring in the lung, loss of function and long-term problems with breathing and maintaining normal activity. In rare cases, people can die of sarcoidosis, but this is very unusual.
Sarcoidosis affects all ages, races and sexes, although there is a slightly higher risk to people of Afro Caribbean descent.
What symptoms does sarcoidosis cause?
The most typical symptoms of cough, breathlessness, feeling very tired and losing weight are usual in the 90% of people with sarcoidosis who have inflammation in the lungs. The severity of sarcoidosis and the extent of lung involvement are usually assessed by spirometry, the same test that is performed on people with asthma and COPD.
Generally, other sarcoidosis symptoms depend on how long the condition has been active, which parts of the body are affected, the number and size of the granulomas, and whether they are growing or beginning to shrink. Other commonly affected parts of the body include:
Lymph nodes: the lymph nodes of the chest are usually the first to become enlarged
Skin: all areas can be affected, but sarcoidosis usually affects the skin on the lower legs and face. There are often painful red or purple swellings. When they occur on the legs they are known as erythema nodosum
Eyes: any of the tissues in the eye may become inflamed, causing red, watery eyes. More serious consequences include a loss of visual acuity, glaucoma and in extreme cases, cataracts and blindness
Internal organs: the liver, spleen and heart can all be affected
Joints: the knees are particularly affected and become swollen and painful because of arthritic changes.
Why diagnosing sarcoidosis can be difficult
Accurate, early diagnosis of sarcoidosis can be difficult because the signs of the disease are vague and many other conditions cause similar symptoms. A diagnosis of sarcoidosis can only be made after the many other conditions have been eliminated, including tuberculosis, farmer’s lung (hypersensitivity pneumonitis), lymphoma (cancer of the lymph nodes), fungal infections, rheumatic fever and rheumatoid arthritis.
There is no single definitive test for sarcoidosis but diagnostic tests that can be done include:
An X-ray or CT scan: granulomas may show up clearly in the lungs or surrounding lymph nodes. Imaging can also reveal the extent of lung fibrosis that has occurred
A biopsy: taking a sample of affected tissue can confirm the presence of granulomas. Lung biopsies are quite invasive, so an alternative is to have a lung lavage. This involves taking fluid samples rather than tissue from areas that look inflamed in CT imaging; if the fluid has very high levels of white cells, this strongly suggests sarcoidosis
Blood tests that look for elevated levels of angiotensin converting enzyme: approximately a quarter of people with sarcoidosis will have high levels of this enzyme, but if it is normal that does not mean sarcoidosis can be ruled out.
Can sarcoidosis be treated?
In very mild cases of sarcoidosis the only treatment needed is monitoring of the symptoms to make sure the lungs are not sustaining significant damage. The condition may clear up without any medical intervention. Regular check-ups will involve the X-rays, scans and blood tests listed above. Mild symptoms can be treated with non-steroidal anti-inflammatory drugs such as ibuprofen.
If treatment is needed, the basic aim is to reduce the size of the granulomas, thereby preventing scarring and damage to vital organs. Inflammation can generally be treated with steroids such as prednisone, and most cases of sarcoidosis respond well. If the granulomas are accessible – on the skin for example – steroids can be applied directly. Otherwise, systemic steroids will be prescribed.
Steroid use presents a bit of a catch-22 situation. Prolonged use of steroids can have side effects, but if treatment is stopped too soon the granulomas can return. The most effective solution is to use a high dose for a short time, followed by a lower dose for at least a year.
For the few people whose sarcoidosis gets worse despite prolonged steroid treatment, immunosuppressant drugs can be used to reduce the immune response that causes the granulomas.