Aspergillosis

Aspergillus is a mould found in the environment. People inhale its conidia routinely, and intact respiratory defenses usually remove them without illness. The danger changes when immune defenses are substantially impaired, particularly with prolonged neutropenia or after hematopoietic stem-cell transplantation. In that setting, inhaled conidia can germinate into hyphae and produce invasive pulmonary aspergillosis. The invasive form is dangerous because the hyphae can grow through pulmonary blood vessels. This angioinvasion promotes thrombosis, tissue ischaemia, necrosis, and haemorrhage. It explains why a patient may develop pulmonary nodules, a halo of surrounding ground-glass change on CT, haemoptysis, and sudden oxygenation failure. Once the organism enters the circulation, it can disseminate, including to the central nervous system. Not every Aspergillus-related illness is invasive disease. Allergic bronchopulmonary aspergillosis is an immune-mediated airway condition, usually considered in a patient with asthma or cystic fibrosis who has wheeze, mucus plugging, and recurrent pulmonary symptoms. An aspergilloma is a fungus ball growing within a pre-existing lung cavity and may present with haemoptysis without the same pattern of systemic invasion. The host history and clinical trajectory therefore matter...