TABLE 1.

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].