Two species of Aspergillus, A.fumigatus and A.clavatus are dealt with here.

For the clinician, the initial identification of fungal disease is often difficult and is based on a series of diagnostic criteria. In general, three types of bronchopulmonary illness are recognised as associated with Aspergillus fumigatus and images to illustrate these are presented..

An allergic response may occur in asthmatic patients, involving eosinophilia, positive immediate skin tests to Aspergillus antigens and increased levels of IgE. Plugs(casts) containing mycelial colonies may be expectorated in sputum and cultures can be easily grown for identification. Much fungal development here seems to be saprophytic and little if any active colonisation of lung parenchyma takes place.

The colonisation of an old pre-existing lung cavity from earlier respiratory disease can give rise to a fungus ball(Aspergilloma). This also represents saprophytic involvement usually with lack of fungal growth into adjoining lung tissue.

Invasive infection develops when the fungus directly colonises lung parenchyma from which haematogenous dissemination may then cause sytemic disease involving distant organs such as the kidney, the heart and nervous system. These infections directly involve immunocompromised patients who are receiving immunosuppressive drugs or steroids. Less commonly Aspergillus flavus may also be the fungus involved. Nosocomial aspergillosis is significant in groups of patients undergoing organ transplantation and accompanying chemotherapy. It can also follow agranulocytopenia in patients being treated for AIDS.

Precipitating antibody(IgG) tests are routinely used as a means of identifying a patient's exposure to and/or infection by Aspergillus fumigatus.

Extrinsic allergic alveolitis(Hypersensitivity Pneumonitis) is another known response to repeated inhalations of high concentrations of fungal conidia. In the Aspergilli it is associated with Aspergillus clavatus. The disease in this case is characterised by an Arthus type reaction involving IgG and complement. Images are presented showing environmental situations and electron micrographs of inflammatory cells and of the phagocytosis of fungal conidia by neutrophil polymorphonuclear leucocytes and macrophages.