Bronchiolitis in association with connective tissue disorders.
In general, lung involvement in connective tissue disorders has not been as well defined as has isolated interstitial lung disease; this applies particularly to bronchiolitis, which occurs infrequently. The low prevalence of bronchiolitis may reflect difficulties in making the diagnosis in mild to moderate disease; at present, most reported disease is severe. This is likely to account for the lack of therapeutic success in obliterative bronchiolitis and in many patients with follicular bronchiolitis. There is a need for earlier intervention if treatment is to be effective, and thus there is a need to refine the noninvasive diagnosis of bronchiolitis. This goal is unlikely to be achieved without the systematic noninvasive evaluation and surveillance of large groups of patients with connective tissue diseases. The role of the pulmonary function laboratory in identifying early bronchiolitis remains entirely uncertain; whether silent "small airways disease," defined physiologically, predicts the eventual development of bronchiolitis is unclear. The reversibility of this asymptomatic lesion with inhaled steroid therapy and the role of inhaled treatment in bronchiolitis, in general, have not been evaluated. More work needs to be done to determine the predictive value of CT appearances and BAL findings, to try to identify a subgroup of patients at greater risk of developing severe bronchiolitis. Further histocompatibility studies may serve as a basis for the selection of patients with an increased likelihood of developing airways disease. The role of open lung biopsy requires further clarification. Better noninvasive evaluation should reduce the need for this invasive procedure; in some patients, however, including those with concomitant interstitial lung disease, histologic assessment will remain an essential component of management. In recent years, in contrast to early reports, it has become apparent that organizing pneumonia has a better prognosis than fibrosing alveolitis in the connective tissue diseases; overall, stability or regression of disease, usually with corticosteroid therapy, was documented in 28 of 39 reported cases. In these patients, a tissue diagnosis serves to identify the need for aggressive therapeutic intervention. Finally, the compilation of larger clinical series would improve our understanding of severe bronchiolitis. This is likely to require multicenter collaboration, which often is impracticable; without this approach, however, the description of bronchiolitis will remain anecdotal.