Diagnostic Approach to SLE Patients with Suspected Infection

Clinical Considerations

Opportunistic infections are a major cause of morbidity and mortality in SLE patients, particularly those on chronic glucocorticoids and immunosuppressive agents like mycophenolate mofetil, according to the European League Against Rheumatism 1, 2
The American College of Rheumatology recommends minimizing glucocorticoids to less than 7.5 mg/day for chronic maintenance, and when possible, withdrawn, to reduce the risk of infection and other adverse outcomes 1
Patients on chronic glucocorticoids above 7.5 mg/day have significantly increased infection risk, as stated by the European League Against Rheumatism 1, 2
The differential diagnosis for SLE patients with fever, hypoxemia, and bilateral infiltrates includes Pneumocystis jirovecii pneumonia, cytomegalovirus pneumonitis, bacterial pneumonia, fungal infections, and lupus pneumonitis, according to the American Thoracic Society 2, 3

Bronchoscopy with bronchoalveolar lavage (BAL) is recommended to evaluate for bacterial cultures, Pneumocystis jirovecii, fungal cultures, and viral studies, as suggested by the Infectious Diseases Society of America 2, 3
Blood cultures and respiratory viral panel should be sent while awaiting bronchoscopy results, according to the American College of Chest Physicians 2

The current immunosuppression regimen should be continued without escalation until infection is excluded, as recommended by the European League Against Rheumatism 1
Empiric antimicrobial coverage may be considered based on clinical severity and local epidemiology, according to the Infectious Diseases Society of America 1
If infection is identified, treatment with antimicrobials should be initiated, and consideration should be given to temporary reduction or holding of mycophenolate mofetil, as stated by the American College of Rheumatology 1, 2

If infection is excluded and lupus pneumonitis is confirmed, pulse methylprednisolone followed by higher-dose oral glucocorticoids may be considered, according to the American College of Rheumatology 1
Cyclophosphamide may be added or increased for severe organ-threatening disease, as recommended by the European League Against Rheumatism 1

Escalating immunosuppression in a febrile patient with pulmonary infiltrates without excluding infection first is a potentially fatal error, as warned by the American College of Rheumatology 2
Relying solely on imaging characteristics to distinguish infection from lupus pneumonitis is not recommended, as they can be indistinguishable, according to the American Thoracic Society 3