Desquamative interstitial pneumonia and respiratory bronchiolitis-associated interstitial lung disease

Smoking-related interstitial lung diseases: radiologic-pathologic correlation

Smoking-related interstitial lung diseases (SRILD) are a heterogeneous group of entities of unknown cause. These diseases include desquamative interstitial pneumonia (DIP), respiratory-bronchiolitis-related interstitial lung disease (RB-ILD), pulmonary Langerhans' cell histiocytosis (LCH) and idiopathic pulmonary fibrosis (IPF). High-resolution CT is highly sensitive in the detection of abnormalities in the lung parenchyma and airways. Ground-glass attenuation can occur in DIP and RB-ILD. Whereas DIP is histologically characterized by intra-alveolar pigmented macrophages, RB-ILD shows alveolar macrophages in a patchy peribronchiolar distribution. LCH shows nodular infiltrates on histopathological examination containing varying amounts of characteristic Langerhans' histiocytes. The HRCT findings are characteristically bilateral, symmetrical and diffuse, involving the upper lobe zones with sparing of the costophrenic angles. The most prominent CT features are nodules (sometimes cavitary) measuring 1 to 10 mm in diameter, cysts and areas of ground-glass attenuation. Pathologically, IPF is characterized by its heterogeneity with areas of normal lung, alveolitis and end-stage fibrosis shown in the same biopsy specimen. High-resolution CT findings consist of honeycombing, traction bronchiectasis and intralobular interstitial thickening with subpleural and lower lung predominance. Since coexisting lesions in the same cases have been observed, a better understanding of the different smoking-related interstitial lung diseases (SRILD) allows a more confident and specific diagnosis.

Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually fatal pulmonary disease for which there are no proven drug therapies. Anti-inflammatory and immunosuppressive agents have been largely ineffective. The precise relationship of IPF to other idiopathic interstitial pneumonias (IIPs) is not known, despite the observation that different histopathologic patterns of IIP may coexist in the same patient. We propose that these different histopathologic 'reaction' patterns may be determined by complex interactions between host and environmental factors that alter the local alveolar milieu. Recent paradigms in IPF pathogenesis have focused on dysregulated epithelial-mesenchymal interactions, an imbalance in T(H)1/T(H)2 cytokine profile and potential roles for aberrant angiogenesis. In this review, we discuss these evolving concepts in disease pathogenesis and emerging therapies designed to target pro-fibrogenic pathways in IPF.

Lack of evidence for an association between neurofibromatosis and pulmonary fibrosis

STUDY OBJECTIVES

To reassess the association between neurofibromatosis and pulmonary fibrosis.

DESIGN

Retrospective single-center study with analysis of patients' chest radiographs, CT scans, and medical records.

SETTING

Tertiary care, referral medical center.

PATIENTS

One hundred fifty-six adult patients with neurofibromatosis seen over a 6-year period between 1997 and 2002.

RESULTS

A review of chest radiographs revealed abnormal findings in 70 patients (44.9%). The most common radiographic abnormalities were extrapulmonary nodules or masses seen in 22 patients (14.1%), followed by skeletal abnormalities in 16 patients (10.3%). Bilateral interstitial infiltrates were noted in only three patients (1.9%), all of whom had potential causes other than neurofibromatosis for their lung infiltrates, including smoking-related interstitial lung disease, rheumatoid lung disease, recurrent pneumonias, and a history of ARDS. CT scans were available in two of these patients and revealed nonspecific patterns of abnormalities with no honeycombing. Six patients had bullae or cystic airspaces demonstrated on chest radiography or CT scan; all of these findings occurred in the context of smoking-related emphysema. Combined together, bilateral interstitial lung infiltrates or cystic airspaces were demonstrated in five patients (3.2%) by chest radiography, and in eight patients (5.1%) by chest radiography or CT scanning; one patient had both findings on the CT scan.

CONCLUSIONS

We found little evidence to support an association between neurofibromatosis and pulmonary fibrosis or any other form of parenchymal lung disease. Interstitial lung disease and bullae described in association with neurofibromatosis in previous reports may have, in part, represented smoking-induced manifestations.