Asymptomatic bacteriuria as a warning sign of purulent pericardial effusion in a patient with systemic lupus erythematosus: a case report

BACKGROUND: Purulent pericardial effusions are rare, comprising less than 1% of pericardial disease. Patients with systemic lupus erythematosus are particularly vulnerable owing to immunosuppression, and distinguishing infectious from autoimmune causes of pericardial effusion can be challenging. This distinction is critical, as treating a flare with immunosuppression can worsen an occult infection. We describe a unique case of a patient with systemic lupus erythematosus who developed purulent pericardial effusion secondary to methicillin-sensitive Staphylococcus aureus, and we highlight asymptomatic bacteriuria as a potential early indicator of this process. To our knowledge, this is the first reported case of purulent pericardial effusion preceded by methicillin-sensitive Staphylococcus aureus bacteriuria in a patient with systemic lupus erythematosus. CASE PRESENTATION: A 45-year-old African-American woman with systemic lupus erythematosus presented with joint pain, pleuritic chest pain, and malaise. She was initially treated for a presumed systemic lupus erythematosus flare. She was also found to have a small-moderate pericardial effusion and asymptomatic methicillin-sensitive Staphylococcus aureus bacteriuria. Days later, she developed acute encephalopathy, respiratory distress, and hemodynamic instability. Blood cultures grew methicillin-sensitive Staphylococcus aureus, transthoracic echocardiogram revealed mitral valve vegetations consistent with infective endocarditis, and brain imaging showed septic emboli. Despite appropriate antibiotics, the patient's pericardial effusion enlarged and required pericardiocentesis, yielding purulent fluid which grew methicillin-sensitive Staphylococcus aureus. The effusion recurred, eventually prompting pericardial window surgery. Postoperatively, the patient's mental and functional status continued to improve, and she was discharged to a long-term care facility. Repeat transthoracic echocardiogram 6 weeks after discharge showed a small pericardial effusion and a normal ejection fraction. CONCLUSION: This case highlights an atypical presentation of purulent pericardial effusion due to methicillin-sensitive Staphylococcus aureus in a patient with systemic lupus erythematosus. Purulent pericardial effusions can present with nonspecific symptoms, and the diagnosis may be obscured in critically ill patients with multiple active processes contributing to a shock state. As methicillin-sensitive Staphylococcus aureus is an uncommon bacteria to be found in the urine, it may be a warning sign of disseminated infection in immunocompromised patients and should prompt further work-up. In addition, point-of-care ultrasound can serve as a valuable tool in identifying tamponade physiology and prompting timely intervention. Clinicians should be alert to the possibility of purulent pericardial effusion in immunocompromised patients with methicillin-sensitive Staphylococcus aureus bacteremia.