What is the most likely underlying process to have created the cavity the fungus ball now inhabits?
Pulmonary tuberculosis is most common, accounting for 25 - 80% of cases depending on the prevalence of TB in the population.
What are some other causes of cavities that can become colonised by fungi?
Pulmonary sarcoidosis, cystic bronchiectasis from any cause, bronchogenic cyst, pulmonary sequestration, pneumatocoeles.
What is the most serious complication which is encountered in these patients?
Haemoptysis.
What treatment is required?
An asymptomatic aspergilloma does not necessarily require treatment, and the cavity is essentially isolated from any systemic administration of anti-fungals. In the setting of brisk haemoptysis, angiography may be performed on an emergency basis and selective bronchial artery embolisation can be life saving. Failing this, or in cases of repeated haemoptysis surgical excision with a lobectomy remains the gold standard.
On the CT scan the right upper lobe density had the classical appearance of an aspergilloma: a well formed cavity with a central soft tissue attenuating rounded mass surrounded by an air crescent sign.