Prevalence and clinical features of rheumatoid arthritis (RA)-associated lung diseases
| Disease phenotype | Clinical features | Prevalence |
| Parenchymal lung disease | ||
| UIP pattern | Radiographic pattern: subpleural, basal predominant reticular opacities, honeycombing, minimal ground-glass opacity, architectural distortion with traction bronchiectasis Associated with worse outcomes compared to other disease patterns in RA | 8–66% |
| NSIP pattern | Extensive ground-glass opacity, traction bronchiectasis, subpleural sparing Lower risk of disease progression and better treatment response compared with UIP | 19–57% |
| Organising pneumonia | Focal ground-glass opacities, consolidations, reversed halo sign | 0–11% |
| Other (e.g. LIP or DIP) | Thin-walled cysts, centrilobular nodules, ground-glass attenuation, peribronchovascular septal thickening, upper-lobe predominant | Rare |
| Rheumatoid nodules | May be single or multiple and range in size, typically asymptomatic unless they cavitate or rupture, in which case infection, pleural effusion or bronchopleural fistula may occur | <1% radiographically, 30% on autopsy specimens |
| Caplan's syndrome | Complication that occurs in those with pneumoconiosis from occupational exposure to coal, silica or asbestos Sudden development of multiple nodules, from 0.5 to several centimetres in diameter, distributed throughout the lungs but predominantly at the lung periphery | <1% in the USA by autopsy |
| Airway disease | ||
| Upper airway | ||
| Cricoarytenoiditis | Arthritis of the cricoarytenoid joint leading to mid-line adduction of vocal cords with resultant hoarseness and/or stridor | 32–75% via laryngoscopy 54–72% on CT scans |
| Lower airway | ||
| Bronchiectasis | Associated with chronic infection | Present on HRCT in ∼30%, though many cases clinically silent |
| Bronchiolitis (constrictive or follicular) | Female sex, high RF titre and long disease duration | By pulmonary function testing or radiographic pattern: 8–30% |
| Pleural disease | ||
| Pleural effusion | Middle-aged males with positive RF and rheumatoid nodules Rheumatoid effusion: classically sterile, exudative fluid with low pH (<7.3), glucose <60, and elevated LDH | Symptomatic in 3–5%, though present in up to 70% in autopsy studies |
UIP: usual interstitial pneumonia; NSIP: nonspecific interstitial pneumonia; LIP: lymphocytic interstitial pneumonia; DIP: desquamative interstitial pneumonia; CT: computed tomography; HRCT: high-resolution CT; RF: rheumatoid factor; LDH: lactate dehydrogenase. Data from [9, 10, 12–21].