Aspergillus

Question 1

Define

Answer 1

• Aspergillosis is an infection caused by the fungus Aspergillus
• Describes a large number of lung disease involving both infection and growth of the fungus as well as allergic responses

→Aspergillus produces a toxin called aflatoxin which contaminates nuts, grains and rice (leads to mycotoxicosis)

Question 2

Causes

Answer 2

The group of fungi affect the lung in 5 ways:

(1) Asthma - type 1 hypersensitivity (atopic) rxn to fungal spores

Severe asthma with fungal sensitisation

(2) Allergic broncho-pulmonary Aspergillosis (ABPA)

• Colonisation of the airways by Aspergillus leads to IgE and IgG-mediated immune responses
• Occurs more frequently in pts with asthma and allergies: Affects 1-2% of asthmatic and 2-25% of CF
• The release of proteolytic enzymes, mycotoxins and antibodies leads to airway damage and central bronchiectasis
• Bronchoconstriction seen early on (allergic reaction), progressing to bronchiectasis as a result of persistent inflammation and permeant damage

(3) Aspergilloma (mycetoma)

• Growth of an A. fumigates mycetoma ball in a pre-existing lung cavity (e.g. post-TB, old infarct or abscess)
• Often caused by TB or sarcoidosis (or CF)
• Usually asymptomatic but may cause cough, haemoptysis, lethargy, weight loss (wide range of severity) Examination → if large may cause tracheal deviation

(4) Invasive Aspergillosis

• Invasion into lung tissue and fungal dissemination
• Risk factors  immunocompromised e.g. neutropaenia, steroids, transplantation, AIDS, leukaemia, burns, Wegener’s (granulomatosis with polyangitis, GPA), SLE or following broad- spectrum antibiotic therapy
• May disseminate to other organs (brain, skin)
• Presentation: dyspnoea, fever, cough, pleuritic pain → Rapid deterioration with a septic picture
• Can be fatal if not treated early and aggressively
• Examination → cyanosis may develop

(5) Extrinsic allergic alveolitis (EAA)
* May be caused by sensitivity to Aspergillus clavatus (‘malt worker’s’ lung) – diagnosis based on history of exposure and presence of serum precipitins to A.clavatus

Question 3

Epidemiology

Answer 3

• UNCOMMON
• Mainly occurs in the ELDERLY and IMMUNOCOMPROMISED

Question 4

Symptoms

Answer 4

Aspergilloma

• ASYMPTOMATIC
• Haemoptysis (potentially massive)

ABPA

• Difficult to control asthma
• Recurrent episodes of pneumonia with wheeze, cough, fever and malaise

Invasive Aspergillosis

• Dyspnoea
• Rapid deterioration
• Septic picture

Question 5

Signs

Answer 5

• Tracheal deviation (only with very large aspergillomas)
• Dullness in affected lung
• Reduced breath sounds
• Wheeze (in ABPA)
• Cyanosis (possible in invasive aspergillosis)

Question 6

Investigations

Answer 6

Aspergilloma

• CXR
  
  • May show a round mass with a crescent of air around it
  • Usually found in the upper lobes
• CT or MRI - may be used if CXR is unclear

NOTE: sputum cultures may be negative if there is no communication between the cavity colonised by Aspergillus and the bronchial tree

ABPA

• Immediate skin test reactivity to Aspergillus antigens
• Eosinophilia
• Raised total serum IgE
• Raised specific serum IgE and IgG to A. fumigatus
• CXR
  
  • Transient patchy shadows
  • Collapse
  • Distended mucous-filled bronchi
  • Signs of complications:
  • Fibrosis in upper lobes
  • Bronchiectasis
• CT
  
  • Lung infiltrates
  • Central bronchiectasis
• Lung Function Tests
  
  • Reversible airflow limitation
  • Reduced lung volumes/gas transfer

Invasive Aspergillosis

• Aspergillus is detected in cultures or by histological examination
• Bronchoalveolar lavage fluid or sputum may be used diagnostically
• Chest CT
  
  • Nodules surrounded by a ground-glass appearance (halo sign)
  • This is caused by haemorrhage into the tissue surrounding the fungal invasion