29th July 2023

Aspergillosis

Aspergillosis refers to the infection caused by moulds belonging to the genus Aspergillus. Hundreds of species of Aspergillus exist in nature, and many can cause disease in humans, but over half of all cases of invasive aspergillosis are caused by Aspergillus fumigatus.

Aspergillus is found worldwide and is particularly associated with decomposing vegetable material (e.g. mulch). Humans inhale aspergillus spores frequently without disease occurring. In general, there needs to be a background of immunosuppression or chronic lung disease (e.g. asthma) for aspergillosis to occur.

Aspergillosis is not contagious, and spores cannot be passed from one person to another.

A range of disease syndromes caused by aspergillus can occur; the most clinically important include:

• Allergic bronchopulmonary aspergillosis (ABPA)
• Chronic pulmonary aspergillosis (including aspergilloma)
• Invasive aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA)

ABPA occurs most often in individuals with underlying asthma or cystic fibrosis due to a hypersensitivity reaction to inhaling Aspergillus spores.

The clinical presentation is similar to an acute exacerbation of asthma or a severe allergic reaction – characterised by wheezing, cough and shortness of breath.

It is associated with bronchiectasis, which is a potential chest X-ray finding. Characteristically, patients will demonstrate marked eosinophilia on blood tests. Radioallergosorbent (RAST) tests and Aspergillus-specific IgE serum tests can also be done to confirm the diagnosis.

First line treatment is with oral corticosteroids, with itraconazole used as the second line for cases which fail to respond to initial treatment.

Chronic pulmonary aspergillosis (and aspergilloma)

In which aspergillosis leads to fibrosis of the lungs, cavitation, and pleural thickening. Chronic pulmonary aspergillosis encompasses several diseases, such as aspergilloma, chronic cavitary pulmonary aspergillosis, chronic fibrosing pulmonary aspergillosis, and subacute invasive pulmonary aspergillosis. Aspergilloma is explored in greater detail below and is a frequent MRCP question.

Patients typically present with a chronic respiratory illness similar to bronchiectasis or COPD – chronic productive cough, wheeze, dyspnea – with intermittent episodic flare-ups marked by more acute symptoms and systemic upset. The condition may also be asymptomatic for long periods.

If asymptomatic, many cases can be managed with watchful-waiting, and vigilance for developing any complications. Steroids and antifungals may be used if a patient presents with acute symptoms. Chronic pulmonary aspergillosis is also associated with secondary bacterial chest infections, which are appropriately treated with antibiotics.

The condition can recur after treatment, so long-term monitoring and follow-up are essential.

Aspergilloma

An aspergilloma is a type of mycetoma – a ball of fungal material which forms a mass. They typically form in pre-existing lung cavities and are associated with a previous history of emphysema, tuberculosis and other cavitating lung diseases.

Most people with aspergillomas are asymptomatic, but they can cause a respiratory illness of wheezing, chronic cough, chest pain, haemoptysis and malaise. It is, therefore, an important differential diagnosis for this collection of symptoms.

Diagnosis is through chest x-ray, which will demonstrate the aspergilloma. The serum testing mentioned previously can be used to screen for Aspergillus. A definitive diagnosis can be made with a biopsy and fungal culture to confirm the aetiology.

Management is of chronic pulmonary aspergillosis, as outlined above.

Invasive aspergillosis

The most severe form of the disease will typically only infect immunocompromised patients. Infection typically begins with pulmonary manifestations and may disseminate to various organ systems, such as the kidneys, heart, skin and CNS, where it can cause a meningitic illness. It is also a cause of endocarditis, and haematogenous spread is associated with endophthalmitis of the eye (inflammation of the intraocular fluids).

Regardless of the site affected, the patient will present with a systemic illness of fever, malaise, and sometimes rigors. Life-threatening complications such as sepsis, mass haemoptysis, kidney and liver failure, and airway obstruction may occur.

Diagnosis is confirmed with serological testing for Aspergillus.

Management is with high dose IV antifungals, such as voriconazole. Second line options include caspofungin and amphotericin B for cases which do not respond to initial treatment. Evidence increasingly suggests better outcomes with a combination of voriconazole and caspofungin, which is now generally first line management.

Pulmonary artery embolisation – and even surgery – may be required to manage severe or persistent haemoptysis.