An entire issue of Clinics in Chest Medicine last year was devoted to this topic. Although much overlap exists, specific pulmonary syndromes are characteristic of specific diseases. Here is a selection of some of the more typical examples. This list is not comprehensive and access to the full text of the entire issue is recommended. Although infections (particularly opportunistic) and pulmonary toxicities of anti-rheumatic drugs are not emphasized here they are important in the differential diagnosis.
Systemic sclerosis (SSc)
Interstitial lung disease---various histologic patterns.
Pulmonary hypertension (PAH)---believed to be more common in lcSSc (formerly CREST) than in dcSSc (formerly PSS) but this belief is in dispute.
Pleural disease---fibrosis, may be clinically silent. Effusions rare.
Chronic aspiration of gastric contents (with esophageal dysmotility).
Pneumonia risk (with myositis overlap).
Mixed connective tissue disease (MCTD)
Though often confused with terms like “overlap syndrome” this is best viewed as a distinct entity characterized by the presence of antibodies to a particular ribonuclear protein (RNP).
ILD---incidence and prevalence poorly defined, due in part to confusion about the definition of the disease itself.
PAH---similar to that of SSc.
Pleural disease---in contrast to SSc, (and more like SLE), effusions are common.
Diffuse alveolar hemorrhage (DAH)---similar to SLE.
Rheumatoid arthritis (RA)
ILD---multiple histologic patterns.
Airway disease---cricoarytenoid arthritis, bronchiolitis obliterans and multiple other processes in the lower airways difficult for clinicians to distinguish from COPD and often coexisting with ILD.
Nodules---solitary or multiple.
Caplan syndrome---RA + any of a variety of pneumoconioses, manifesting as the rapid appearance of multiple pulmonary nodules, some with cavitation. Mainly of historical interest.
Systemic lupus erythematosis (SLE)
Acute lupus pneumonitis---rare; high mortality; may present like pneumonia or as ARDS. Treated with steroids, associated with anti-double stranded DNA.
Chronic ILD---its strong association with anti-SSA has led to dispute over whether these patients represent Sjogren's or overlap.
Shrinking lung syndrome---sometimes confused with, but to be distinguished from, vanishing lung syndrome. Physiologically characterized by low lung volumes and elevated diaphragms. Unclear whether myopathic, neuropathic or both.
ARDS---not a specific entity, but can occur from acute lupus pneumonitis, DAH or infections. (See here regarding “atypical” forms of ARDS, ie ARDS as a manifestation of specific diseases).
Pulmonary vascular disease---PAH if overlap syndrome, PTE if anti-phospholipid syndrome coexists.
Airway disease---dryness, lymphocytic exocrinitis.
PAH, pleural disease rare.
Pneumonia risk, said to be “aspiration” pneumonia. “Aspiration” is in quotes because of the meaningless way in which the term is commonly used in pulmonary medicine. Note that almost all bacterial pneumonias, even in healthy hosts, are caused by aspiration of colonizing flora. It would be more accurate to say that patients with myositis are at risk for pneumonia due to weakness of pharyngeal muscles and difficulty clearing secretions and colonizing flora. Note too that some of these pneumonias are due to treatment related opportunistic infections. In those cases inhalation or hematogenous seeding are more likely to be the inciting event as opposed to aspiration.
ILD---I blogged about myositis associated ILD here.
The main ones are Wegener's, microscopic polyangiitis (MPA) and Churg-Strauss vasculitis.
ARDS (when anti-phospholipid syndrome becomes catastrophic anti-phospholipid syndrome).
Restrictive defect---fusion of chest wall joints.
Apical fibrocystic disease---superinfection of apical disease is common, particularly with non-tuberculous mycobacteria and aspergillus.