Usual interstitial pneumonia (UIP)
Age 55–60, slight male predominance. Insidious dry cough and dyspnea lasting months to years. Clubbing present at diagnosis in 25–50%. Diffuse fine late inspiratory crackles on lung auscultation. Restrictive ventilatory defect and reduced diffusing capacity on pulmonary function tests. ANA and RF positive in ~25% in the absence of documented collagen-vascular disease.
|Patchy, temporally and geographically nonuniform distribution of fibrosis, honeycomb change, and normal lung. Type I pneumocytes are lost, and there is proliferation of alveolar type II cells. “Fibroblast foci” of actively proliferating fibroblasts and myofibroblasts. Inflammation is generally mild and consists of small lymphocytes. Intra-alveolar macrophage accumulation is present but is not a prominent feature. ||Diminished lung volume. Increased linear or reticular bibasilar and subpleural opacities. Unilateral disease is rare. High-resolution CT scanning shows minimal ground-glass and variable honeycomb change. Areas of normal lung may be adjacent to areas of advanced fibrosis. Between 2% and 10% have normal chest radiographs and high-resolution CT scans on diagnosis. ||No randomized study has demonstrated improved survival compared with untreated patients. Inexorably progressive. Median survival approximately 3 years, depending on stage at presentation. Nintedanib and pirfenidone reduce rate of decline in lung function. |
Respiratory bronchiolitis-associated interstitial lung disease (RB-ILD)1
Age 40–45. Presentation similar to that of UIP though in younger patients. Similar results on pulmonary function tests, but less severe abnormalities. Patients with respiratory bronchiolitis are invariably heavy smokers.
|Increased numbers of macrophages evenly dispersed within the alveolar spaces. Rare fibroblast foci, little fibrosis, minimal honeycomb change. In RB-ILD the accumulation of macrophages is localized within the peribronchiolar air spaces; in DIP1, it is diffuse. Alveolar architecture is preserved. ||May be indistinguishable from UIP. More often presents with a nodular or reticulonodular pattern. Honeycombing rare. High-resolution CT more likely to reveal diffuse ground-glass opacities and upper lobe emphysema. ||Spontaneous remission occurs in up to 20% of patients, so natural history unclear. Smoking cessation is essential. Prognosis clearly better than that of UIP: median survival greater than 10 ...|