"Infection with Aspergillus spp. occurs in up to 10% of patients who underwent allogeneic stem cell transplantation 5,6. Aspergillus, unlike other pulmonary infections, can infect the lung at any stage following stem cell transfusion 6."
"Spores of a variety of Aspergillus spp. are inhaled and begin to proliferate in the alveoli. The hyphae are able to invade pulmonary arteries resulting in pulmonary necrosis and haemorrhage 1. They may also gain access to the systemic circulation and are haematologically-disseminated to the kidneys, gastrointestinal tract, and the central nervous system. Systemic dissemination occurs in 25-50% of cases 1."
"If the neutrophil count recovers (in patients where neutropenia is the cause of the immunosuppression), the central necrotic area of lung demarcates, shrinks and separates from the adjacent viable tissue. It is this separation that creates the air crescent sign 6."