SLE and lung disease

Lupus can present in many ways, involving nearly any organ in the body. Pulmonary complaints are common in lupus and take on different forms. 

Pleural disease can present with chest pain with inspiration, a symptom described in nearly 50% of SLE patients at some point in their disease. Pleuritis can be identified with a rub on clinical exam and may or may not be associated with a pleural effusion. When present, pleural effusions in SLE are typically exudative, with low glucose, low complement levels and positivity for ANA. This disease is usually mild and can be treated with anti-inflammatory medication. However, it has been associated with additional lung disease in SLE including the shrinking lung sydrome (SLS - see below).

Pulmonary infections should be considered, given the relative immunosuppression in SLE patients as well as their typical immunosuppressing drug regiments, these patients are increased risk for infection. Infections typically present as they would in patients without SLE, with cough, dyspnea, and fever. A study looking at risk factors for infection in SLE identified corticosteroids and renal disease as risk factors, and found no association with leukopenia or azathioprine use in isolation. 

Pneumonitis is an uncommon but serious complication of SLE (~1-4%). Short term mortality can reach upwards of 50%. Patients present with significant respiratory symtpoms and ground glass opacities on CT scan, usually bilaterally. This is treated with immunosuppressant, sometimes requiring pulse steroids. 

Interstitial lung disease can occur in up to 10% of patients with SLE. It tends to be a subacute presentation with dyspnea, cough and exertional symtpoms. There is variability in this clinical presentation, where patients may have a fibrotic or inflammatory pattern on imaging. Most commonly patients will have ground glass on CT scans suggesting a non-specific interstitial pneumonia (NSIP) pattern. Those with the fibrotic form can have imaging similar to that of idiopathic pulmonary fibrosis, which is termed a usual interstitial pneumonia (UIP) pattern. Sometimes a lung biopsy is required to confirm the diagnosis, and bronchoscopy can be useufl in excluding infection.

Pulmonary hypertension is a known complication of SLE. It has a similar pathophysiology to that of primary arterial hypertension, which is different than that of left sided heart failure and chronic venous thromboembolic disease. However, as noted in morning report today, patients with SLE may have anti-phospholipid antibodies, putting them at risk for thrombosis and PE. Treatment may require vasodilating agents like bosentan or sildenafil.

Shrinking lung syndrome, characterized by decreasing lung volumes, dyspnea and chest pain. It is felt to be a relatively rare condition, though patients may not be monitored for this disease appropriately with repeated lung volumes. The mechanism may involve worsening diaphragmatic dysfunction though this is somewhat controversial. Some data suggests that nerve conduction to the diaphragm or even chest wall disease may be responsible as opposed to true myopathy of the diaphragm. There have also been multiple studies associating pleural inflammation with development of SLS, pointing to an additional mechanism.

Pulmonary hemorrhage tends to be a more commonly recognized presentation of other rheumatologic conditions (granulomatous polyangiitis, goodpastures syndrome etc), but can rarely occur in SLE. This was documented in 4% of SLE patients in a study spanning ten years. There was a strong association with pulmonary hemorrhage and nephritis, where only one patient who had pulmonary hemorrhage did not have renal involvment. Imaging and bronchoscopy are often indicated to support the diagnosis. 

Acute reversible hypoxemia is a relatively new entity described in the early 1990's. Patient experience transient hypoxemia as a result of leukocyte agreggation and vascular occlusion, which is felt to result from hypercomplementemia and leukocyte activation. See one of the initial articles below from the annals of internal medicine.

Lung disease and SLE

Acute reversible hypoxemia and SLE