Nodular Diseases

Abstract

The subacute form of hypersensitivity pneumonitis (HP) tipically presents a nodular pattern. HP represents a group of diffuse granulomatous parenchymal lung diseases caused by the repeated inhalation of, and sensitization to, a broad variety of low molecular weight organic antigens and chemicals. Clinical presentation may be acute (HP, acute) or chronic (HP, chronic) Extrinsic Allergic Alveolitis (EAA) DEMOGRAPHICS The number of responsible inciting antigens is high (more than 300) and new antigens are constantly being identified. The most commonly known diseases are "Farmer's lung", caused by the inhalation of Faeni rectivirgula present in moldy hay and "Bird fancier's lung", caused by exposure to avian proteins. The subacute form of the disease seems to be produced by a less intense exposure to the inciting antigen than occurs in the acute form. Gell and Coombs type III and type IV immune reactions lie at the basis of the immunopathogenesis of the disease The incidence and prevalence of the disease is difficult to estimate, since individual susceptibility, intensity of exposure in different occupational settings, seasons, geographical areas and proximity of industry vary greatly. The prevalence of "Farmer's lung" varies between 2 and 9%, whereas that of "Bird fancier's lung" varies between 6 and 15% Non-smokers are more commonly affected CLINICAL FEATURES Onset in the subacute form is insidious, with symptoms characterized by slowly worsening cough, dyspnea, fatigue, anorexia and weight loss. Acute exacerbation of symptoms occasionally occurs. In contrast to the acute form, clinical history is not always able to identify a temporal correlation (4-12 h) between onset of symptoms and exposure to the inciting agent (e.g. moldy hay, avian proteins, etc.) Diffuse fine bibasilar rales are often noted on physical examination. Patients may present signs of wasting Patterns include moderate-to-severe restrictive defects and mixed restrictive and obstructive defects. There is hypoxemia at rest and D L CO is reduced in most cases