An extrinsic allergic alveolitis involving inflammation of the alveoli within the lung caused by hypersensitivity to the inhalation of organic dust particles derived from either the mushrooms, their spores or the compost in which the mushrooms are grown. It is usually caused by the spores of thermophilic actinomycetes. [ http://purl.obolibrary.org/obo/ECO_0007645 ]