2.2. Fibrosing alveolitis

Fibrosing alveolitis can be idiopathic (King 1998) or associated with various connective tissue diseases, e.g. rheumatoid arthritis (Kelly 1999) and systemic lupus erythematosus (de Andrade & Kennedy 1999). Epidemiological data on idiopathic fibrosing alveolitis are sparse. The prevalence range has been reported to be 6–14.6 per 100000 (Scott et al. 1990, Coultas et al. 1994). The etiology of idiopathic pulmonary fibrosis or cryptogenic fibrosing alveolitis is unknown, but there is evidence to suggest that occupational and environmental factors as well as viral, immunologic, and genetic factors are involved in the development of idiopathic fibrosing alveolitis (King 1998). The clinical features are variable. The condition is seen most often in middle-aged or older adults. The presentation is insidious in most patients with a progressive course of several years, but the onset can also be acute and fulminant. A favourable response to medication, most commonly corticosteroids or cytotoxic therapy, is shown by only in one third of the patients. (Katzenstein & Myers 1998). Idiopathic fibrosing alveolitis was recently classified pathologically by Katzenstein and Myers as follows: 1) Usual interstitial pneumonia (UIP), 2) Desquamative interstitial pneumonia (DIP)/respiratory bronchiolitis interstitial lung disease, 3) Acute interstitial pneumonia (AIP, Hamman-Rich disease) and 4) Non-specific interstitial pneumonia (NSIP) (Katzenstein & Myers 1998). UIP is the most common type of idiopathic fibrosing alveolitis, accounting for over 60% of the cases (Bjoraker et al. 1998). The course of UIP is chronic and the prognosis is poor, with mortality ranging from 59% to 70%. Patients with DIP are usually younger than patients with UIP, and their prognosis is better with mortality of 5% in five years. There is a clear predominance of men in UIP and DIP. The prognosis of AIP is worst with a mortality range of 50% to 80% and most deaths occurring within 1 to 2 months. Mortality from NSIP is 15-20% in five years. To distinguish between these entities, it is recommendable to perform open lung biopsy. (Katzenstein & Myers 1998, King 1998). Currently, there is no single reliable prognostic factor for the activity of cryptogenic fibrosing alveolitis. The follow-up is mostly based on spirometry and diffusion capacity values, chest radiography and occasionally high-resolution computed tomography (HRCT) of the lungs (Johnston et al. 1999).