Acute reversible hypoxemia in systemic lupus erythematosus

Area of Science:

• Pulmonary Medicine
• Rheumatology
• Critical Care

Background:

• Systemic lupus erythematosus (SLE) can affect multiple organs, including the lungs.
• Unexplained hypoxemia in SLE patients may indicate a distinct clinical syndrome.

Purpose of the Study:

• To determine the frequency of unexplained reversible hypoxemia in SLE patients.
• To assess the relationship between hypoxemia and elevated plasma complement split products.

Main Methods:

• A cohort study involving 22 hospitalized SLE patients with disease exacerbation and normal chest X-rays.
• Measurement of plasma complement split products (C3a, factor Bb), alveolar-arterial (A-a) Po2 gradients, and pulmonary function.
• Comparison with SLE patients with stable disease and healthy volunteers.

Main Results:

• Six hospitalized patients experienced episodes of hypoxemia/hypocapnia with elevated A-a gradients.
• These episodes resolved with steroid therapy, accompanied by decreased A-a gradients and C3a levels.
• Elevated C3a levels were significantly higher in patients with hypoxemia compared to those without.

Conclusions:

• A syndrome of reversible hypoxemia, unrelated to parenchymal lung disease, is common in acutely ill SLE patients.
• The pathogenesis is unclear but may involve pulmonary leukoaggregation.
• Complement split products might play a role in the development of hypoxemia in SLE.