RHEUMATOID ARTHRITIS
Rheumatoid arthritis (RA) is a systemic, autoinflammatory disorder defined by its characteristic attack on the diarthroidal joints. It affects approximately 1% of the adult U.S. population, with a two-to-one female pre-dominance. When compared with the general population, overall mortality is increased, with the median survival decreased by 1 decade. A significant portion of the clinical impact of the disease is attributable to its extraarticular manifestations (ExRAs). ExRAs are common, the prevalence of clinically “severe” ExRA ranging up to 40%, and are dominated by cardiac, vascular, and pulmonary disorders.
Up to one-third of RA patients have respiratory
symptoms, and up to two-thirds have chest imaging changes. Physiologic
impairment occurs less frequently, but when present, it is a poor prognostic
sign. Because the medications used to treat RA have been described to cause
both direct pulmonary toxicity as well as increase the risk of infectious
complications, both respiratory infection and drug-induced lung disease should
always be considered in patients with new respiratory symptoms or signs. A
large group of direct RA complications is also well recognized. These complications
can be approached anatomically because they can affect all the compartments of
the chest both in isolation or collectively.
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RA can cause upper, lower, and distal airway disease.
Arthritis of the cricoarytenoid joints, rheumatoid nodules of the upper airway,
and vocal cord paresis all occur. Radiographic bronchiectasis has been
described in up to one-third of patients, but clinically important disease
appears much less frequently. Small airway disease with physiologic obstruction
is common and presents with dyspnea, a nonproductive cough, or wheezing.
Imaging with high-resolution computed tomography (HRCT) demonstrates
centrilobular nodules, hyperinflation, and heterogeneous air trap- ping.
Pathologically, both fibrosing (obliterative or constrictive bronchiolitis)
and cellular (lymphocytic, follicular, and diffuse panbronchiolitis) types of
small airways disease can be seen. Pleurisy, pleuritis, and effusions occur in
approximately 5% of patients and may be the most common symptomatic intrathoracic
manifestation of the disease. The effusions may precede, accompany, or follow
the onset of joint involvement. Despite the preponderance of women with this
disease, rheumatoid pleural effusions are more prevalent in men. They tend to
be small and asymmetric and to wax and wane. Pleural fluid analysis generally
reveals a low glucose level (<50 mg/dL), low pH (<7.30), high
lactate dehydrogenase (LDH) level (>1000 IU/L), and high rheumatoid factor. When
identified, effusions should not be assumed to be RA associated; empyema,
sterile empyema, chylothorax, and congestive heart failure are all seen, but a
fibrothorax with its physiologic restriction and trapped lung are rare.
Isolated, pulmonary hypertension caused by a primary vasculopathy is
exceedingly rare, but capillaritis or alveolar hemorrhage can occur. Rheumatoid
(necrobiotic) nodules are found in up to 20% of patients, typically range from
millimeters to centimeters in size, are usually asymptomatic, and can fluctuate
in size over time. However, they can cavitate and be complicated by
pneumothorax, hydropneumothorax, sterile empyema, and hemoptysis. Nodules
identified on high-resolution computed tomography (HRCT) must be distinguished
from malignant and infectious lesions. Caplan syndrome refers to conglomerations of nodules seen in
patients with RA and pneumoconiosis.
Symptomatic interstitial lung disease (ILD) has been
described in 10% of subjects, but prospective studies using HRCT have shown
specific features of ILD in up to two-thirds. Similar to what is seen with
pleural disease, ILD may precede, accompany, or follow the onset of joint
involvement. Although all of the pathologic patterns described in the
idiopathic interstitial pneumonias
(usual interstitial pneumonia [UIP], nonspecific interstitial pneumonia [NSIP],
organizing pneumonia, diffuse alveolar damage [DAD]) have been described in RA,
unlike most other connective tissue diseases, on surgical lung biopsy a UIP
pattern is more common than the NSIP pattern. The DAD pattern (i.e.,
Hamman-Rich syndrome), is quite uncommon but is impressive with its
presentation as rapid and progressive respiratory failure that frequently
results in death.
