LUPUS: A GP Guide to Diagnosis
Lupus can be considered to affect the lungs in two ways. Firstly, the disease can directly involve the lung itself or lung disease can result more indirectly from infection. Patients with lupus are more susceptible to a wide range of infections. If all the causes of lung disease are grouped together, then involvement of the lung in lupus is quite common. Lupus itself can affect a wide range of tissues in and around the lungs. These various types of lupus-related lung disease are described below on the basis of which parts of the lung are affected.
The lungs are covered in a special layer of tissue termed the pleura, this allows the lungs to move during breathing. These lining tissues can become inflamed, a condition termed pleurisy or pleuritis. Pleurisy is one of the commonest complications of lupus in the lung, affecting up to 50% of patients. Pleurisy is manifest by sharp, stabbing pains in the chest which are aggravated by breathing and moving. In more severe cases a collection of fluid, termed a pleural effusion, can build up in the pleural space around the lungs. Pleurisy can often be treated by aspirin-type anti-inflammatory drugs and/or prednisolone. If a pleural effusion develops, which can usually be seen on a chest X-ray, it is usually advisable to draw off (aspirate) the fluid. This can help alleviate additional symptoms such as breathlessness and can help establish the diagnosis and rule out other causes of a pleural effusion, such as infection.
Although the term pneumonia suggests an infection in the lung, a related term pneumonitis means any type of inflammation in the lung. The reason for making this distinction is that lupus can directly cause lung inflammation (pneumonitis). In addition, lupus can indirectly put people at risk of developing an infective pneumonia.
Direct involvement of the lung in lupus is uncommon. When it does occur, there are two main types of lung disease that can develop, a rapid onset and severe acute pneumonitis and a more insidious, progressive scarring chronic pneumonitis. An acute lupus pneumonitis causes rapid onset of fever, breathlessness, pleuritic pain and sometimes coughing blood (haemoptysis). These symptoms are very similar to those of pulmonary embolism (a blood clot on the lungs which can be indirectly related to lupus as discussed below) and an infective pneumonia. These two complications, pneumonitis and embolism, can be distinguished by a number of tests including chest X-ray, bronchoscopy and other lung scans. A more chronic form of pneumonitis can also occur in lupus. In this situation the patient develops a gradually worsening, slowly progressive breathlessness. This is usually accompanied by changes on the chest X-ray/CT scan and alterations in lung function tests. These tests can be used to help monitor progress of lung disease. Clinical features similar to those of chronic lupus pneumonitis can also be caused by certain lung infections, rare side effects of drugs and lung tumours - tests such as bronchoscopy may be required to exclude some of these other possible diagnoses. Lupus lung disease may be treated with prednisolone and azathioprine or, if very severe, cyclophosphamide.
The "shrinking lungs" syndrome is used to describe an uncommon form of lung disease that can occur in lupus. This complication is characterised by a loss of volume of both lungs manifest by worsening shortness of breath. Breathlessness may be aggravated on lying horizontally. The cause of this syndrome is uncertain, however, there is some evidence that weakness of the breathing muscles contributes to this syndrome. All muscle groups can be affected in lupus, resulting in weakness. It is thought that when the muscles concerned with breathing (the diaphragm which separates the lungs from the abdomen and muscles between the ribs) are affected by weakness the "shrinking lungs" syndrome may result. The best method of treatment for this complication is not known, although some cases do respond to prednisolone.
The lungs have their own separate blood circulation (pulmonary circulation) which is distinct from the circulatory system of the rest of the body (systemic circulation). The pulmonary circulation can develop high blood pressure (pulmonary hypertension). This is different from the usual understanding of the term high blood pressure, when the systemic circulation is primarily affected. The reasons why lupus patients are at risk from pulmonary hypertension are not known. Patients who have more severe Raynaud's phenomenon in the hands/feet appear to be more susceptible to pulmonary hypertension, although it should be emphasised that this is a rare complication of lupus. Pulmonary hypertension can also occur as a consequence of other lupus-related lung diseases such as chronic pneumonitis or pulmonary embolism. This syndrome is associated with breathlessness, a reduced exercise tolerance, and sometimes with effort-associated blackouts. The diagnosis of pulmonary hypertension is made by echocardiography and may require injection of dye into the pulmonary circulation and direct pressure measurements - a pulmonary angiogram.
Some patients with lupus have a tendency to form blood clots. Many of these patients have antibodies in the blood to a variety of different molecules called phospholipids - these being antiphospholipid antibodies or anticardiolipin antibodies. A common place for such blood clots to form is in the veins deep inside the calves. Once formed these clots can grow and fragments of them may break off. Once detached, the clot fragment can be carried through the circulation to the heart and then to the lungs. The fragments then tend to lodge in the small blood vessels in the pulmonary circulation of the lungs. This is termed pulmonary embolism. A large embolus like this can cause chest pain and occasionally the patient may cough up blood. A pulmonary embolus can be difficult to diagnose. A number of tests can help make this diagnosis including a nuclear medicine lung scan and a pulmonary angiogram. The treatment is to make the blood less liable to clot with anticoagulant therapy. Some patients who have a tendency to form blood clots need to be on long term antiplatelet therapy with low-dose aspirin or treated with an anticoagulant drug, such as warfarin.
Patients with lupus are more susceptible to infections for several different reasons. When the disease is active certain types of white blood cells such as lymphocytes do not function properly. Lymphocytes are essential to the functioning of the immune system. Other proteins in the blood which help defend against infectious organisms may also be low in active lupus, such as complement proteins, and the function of the spleen may also be impaired. As well as these factors the drugs used to treat more severe forms of lupus also suppress the immune system. Examples of such drugs include prednisolone, azathioprine and cyclophosphamide. The lung is a relatively common site for infection in states when the immune system is suppressed. Infections may be acute and severe as in certain bacterial pneumonias or they may be more indolent in which case they can mimic a more chronic lung disease. Suspected bacterial lung infections should always be treated promptly with antibiotics and referral to hospital may be indicated.
Finally, an infection may also occur on top of a pre-existing lung disease. Infections can vary quite widely in severity depending on the general health of the patient initially, the nature of the infecting agent and whether there is any underlying lung disease. The treatment is aimed at identifying the causative agent and administering the appropriate antibiotic. Patients on long-term steroid therapy may require a temporary increase in drug dose during the course of an acute infection.
Dr. Timothy J. Vyse |
Dr. Kevin A. Davies |