[Diseases caused by inhalation of organic dusts]

The inhalation of organic dusts can provoke in man various types of diseases, being the respiratory system the most frequently involved. A great number of organic dusts provoke, even in small amounts, in genetically pre-disposed atopic subjects, type I allergic reactions, i.e. bronchial asthma, allergic rhinitis, mediated by IgE reaginic antibodies. On the other hand, a small number of vegetal or animal organic dusts, may provoke type III reactions, mediated by IgG precipitinic antibodies. These reactions can be triggered by a massive and prolonged exposition, probably even in normal subjects and be localized in bronchial tree (precipitnic asthma) or in the pulmonar parenchyma (extrinsic allergic alveolitis). From 5,000 patients observed in the Allergology Unit of the Lisbon University Hospital, a group of 27 cases of extrinsic allergic alveolitis or precipitinic asthma were isolated. This group comprises 21 cases of birds breeders, 4 cases of suberosis, 1 case of yeasts lung and 1 case of seaweed threshing lung. These last two situations have not been previously described and must probably be added to other situations of extrinsic allergic alveolitis described for the first time in Portugal (Vineyard sprayer's lung, furrier's lung). The same type of clinical disease has been observed in 4 patients exposed to inorganic dusts (fuel oil and plastic). In 2 from 21 cases of bird breeder's lung, systemic symptoms without pulmonary manifestations have been observed; in the first patient a thrombocytopenic prupura experimentally reproductible by skin or inhalation tests with a platelet metabolic lesion marked by a decrease in platelet ATP, in the presence of complex of human and bird's serum. Some of these platelet disturbances can be provoked by a vascular lesion in a type III Arthus-like reaction, with intra-vascular coagulation. In another patient with positive precipitins to bird's dropplets and lung histology of the usual pattern in these situations, uveitis has been observed. This uveitis was worsened by skin tests with bird's serum. In a third typical case of birds breeder's disease with positive skin and inhalation tests and positive precipitins, an IgA monoclonal gammapathy has been observed. These patients are always as symptomatic 5 years after the diagnosis. The occurence of thrombocytopenic purpura and monoclonal gammapathy in birds breeder' have probably not been previously reported. An increase in serum immunoglobulins IgA and IgG, but not in IgM has been usually observed in the diseases provoked by inhalation of organic dusts. This pattern reverses after allergen withdrawal. It is possible that the monoclonal gammapathy was related to prolonged antigenic stimulation and proliferation of the IgA producing clone. The increase of immunoglobulins has not been so clear in the some observed cases of inhalation of inorganic dusts. Cellular type IV reactions have been however observed in these patients...