Incidence and clinical signs of pleural involvement in chronic systemic inflammatory diseases
| CTD | Pleural effusion incidence (of CTD patients) | Macroscopic appearance | Clinical signs | |
| Biochemistry | Cytology | |||
| Rheumatoid arthritis | 5–20% | Milky, cloudy, serous or green-yellowish | Exudative effusion, RF titre ≥1:320, Glucose 10–30 mg·dL−1, LDH ≥1000 U·L−1, pH <7.2, High total protein, High cholesterol Single or multiple pleural nodules | Enriched in eosinophils and macrophages (multinucleated) Presence of rheumatoid arthritis cells |
| Systemic lupus erythematosus | 17–60% | Yellow or serosanguineous | Exudative effusion, Glucose 60 mg·dL−1, LDH <500 IU·L−1 pH >7.3 Total protein >3.5 g·dL−1, Antinuclear antibody titres≥1:160 | Enriched in macrophages, neutrophils, basophils, eosinophils and lymphocytes |
| Eosinophilic granulomatosis with polyangiitis | 29% | Exudative effusion | ||
| Granulomatosis with polyangiitis | 5–55% | Exudative effusion Total protein 3.8–5.7 mg·dL−1 | Enriched in neutrophils and other polymorphonuclear cells | |
| Systemic sclerosis | 7% | Exudative effusion pH >7.2 | ||
| Ankylosing spondylitis | Rare | Exudative effusion pH >7.3 Glucose >30 mg·dL−1 | ||
| Sjögren's syndrome | Rare | Exudative effusion Positive titres for RF, antinuclear, anti-Sjögren’s syndrome-A and anti-Sjögren’s syndrome-B antibodies | Enriched in CD3+ and CD20+ B-lymphocytes | |
| Mixed connective tissue disease | 6–50% | Exudative effusion | Enriched in polymorphonuclear leukocytes | |