Although lung (pulmonary) problems are common in systemic lupus they are often not diagnosed until lung disease becomes advanced. Advanced lung disease and pleuropulmonary (affecting the lungs and respiration) problems can significantly contribute to mortality in SLE.
Symptoms and Manifestations
Lung disease (pleurisy) in systemic lupus causes a clinical spectrum of symptoms ranging from mild chest pain to fulminant and rapidly fatal pulmonary hemorrhage.
Inflammation of the pleural sac around the lung (pleurisy), with or withal pleural effusion (excess fluid in the chest cavity) is the most common manifestation in lupus. The pleura is a membrane covering the outside of the lung and the inside of the chest cavity.
Pleural cells produce a small amount of fluid that lubricates the space between the lung and the chest wall. As lupus activity causes the production of immune complexes (formed as antibodies and antigens combine), they complexes initiate an inflammatory response at the pleural membrane. The inflammatory response results in pleuritis.
Pleuritis can cause severe, often sharp, stabbing pain in one or more areas of the chest. Inhaling deeply, coughing, sneezing, or laughing can intensify the pain.
Other pulmonary manifestations frequently seen in SLE include pneumonitis, which refers to inflammation of the lung and pulmonary emboli, which refers to the presence of blood clots in the lung. Pneumonitis, which is usually caused by infectious agents, can cause fever, shortness of breath, chest pain, and cough.
Chronic interstitial lung disease in lupus may cause difficulty breathing during activity, chest pain with symptoms of pleurisy and a chronic dry cough.
Pulmonary embolism can cause chest pain and abnormal oxygen exchange resulting in shortness of breath.
Imaging tests are primarily used to diagnose lung disease. Chest radiographs, ventilation-perfusion lung scans, gallium scans, and high-resolution CT scans are the tests most commonly used. If chest fluid is present, patients may also have a bronchoalveolar lavage in which fluid is aspirated from the chest cavity.
In addition, pulmonary function tests and arterial blood gas levels may be performed. However, it can be difficult to distinguish respiratory problems such as pneumonia from interstitial lung disease in patients with systemic lupus. A microbiology examination on sputum, a bronchoscopy or a lung biopsy may be performed when infectious pneumonitis is suspected.
In the past, pleural fluid was examined for the presence of anti-nuclear antibodies (ANA). Recent studies show that the ANA test is only positive in half of patients with lupus pleurisy. In addition, patients with other pulmonary diseases besides lupus can have a positive ANA.
Diagnostic criteria used in the past, including ANA tests and complement levels, made lupus pleurisy difficult to detect and difficult to manage. New studies suggest that an elevated white blood cell count, the presence of lupus erythematosus (LE) cells, and an elevated level of the enzyme lactic dehydrogenase (LDH) are more consistent findings.
Pulmonary embolism can be ruled out with negative results on a blood test known as the quantitative D-dimer test. However, a positive result can occur in other conditions and doesn’t necessarily mean that pulmonary emboli are present. Other tests used to diagnose pulmonary emboli include ventilation-perfusion (breathing and blood flow) scans of the lung.