Aspergillosis Flashcards
(33 cards)
What are most fungi?
Saprophytes
When are fungi most likely to cause infections?
When immunity is reduced
What are the most common fungal infections?
Dermatophyte infections
- ringworm of the nails
- tinea cruris
- athlete’s foot
- tinea corporis
Which areas of the body does candida affect?
Oral cavity
Oesophagus
Vagina / Glans penis (balanitis)
Systemic (only in immunosuppressed)
When often precedes an oesphageal candida infection?
ABX, Steroids, Immunosuppressants use
What is aspergillus?
A mould - i.e. grows in the form of hyphae (multicellular filaments), can also exist in spore form (unicellular)
What condition is unique to aspergillus inside the body?
Always exists as hyphae due to anaerobic conditions
- except in aspergillomae
What are the two most common fungal pathogens in humans?
- Candida
2. Aspergilluss
What toxin produced by aspergillus causes hepatocellular carcinoma?
Aflatoxin
- produced by aspergillus growing on mouldy peanuts
What are the 4 main presentations of aspergillosis disease?
Allergic bronchopulmonary aspergillosis (hypersensitivity pneumonitis)
Aspergilloma
Chronic granulomatous aspergillus pneumonia
Invasive aspergillosis
Describe the pathophysiology of hypersensitivity pneumonitis (allergic broncho-pulmonary aspergillosis)
Presence of antigen (e.g. aspergillus) in bronchi/alveoli
Produces immune mediated response via 2 pathways
- type 3 hypersensitivity reaction
- type 4 hypersensitivity reaction
Describe a type 3 hypersensitivity reaction?
Immune complex formation
= extensive cross linking by Abs and antigens
- Antiboies => mainly Th2 and B cell mediated
Neutrophil degranulation causing increased vascular permeability
Describe a type 4 hypersensitivity reaction?
Delayed hypersensitivity reaction
= cell mediated immune memory response
- mainly Th1 cells and macrophages
Granulomas and inflammatory damage result
What does allergic broncho-pulmonary aspergillosis result in?
Bronchospasm
Mucous plugging
Bronchocentric inflammation with progressive bronchiectasis, smooth muscle hypertrophy and pulmonary fibrosis
What are the risk factors of allergic-broncho pulmonary aspergillosis?
Underlying lung disease, e.g. asthma, CF, COPD
- clearance of spores more diffucult
What are the symptoms and signs of allergic broncho-pulmonary aspergillosis?
Develops 4-6 hours post-exposure
Fever
Dyspnoea
Cough - productive, occasionally haemoptysis
Wheeze
Sx alleviated after spell without exposure
What are the investigations of allergic broncho-pulmonary aspergillosis?
Peak flow / spirometry
CXR - infiltrates and consolidation
Allergy testing
Broncheolar lavage => raised WCC, Eosinophilsand aspergillus
Bloods => raised IgE, aspergillus Antibodies
VATS biopsy => alveoli filled with macrophages and lymphocytes
How should allergic broncho-pulmonary aspergillosis be treated?
Prevent further exposure to allergen
Oral corticosteroids, e.g. prednisolone
+/- oral antifungals (itraconazole)
Immunosuppresants, e.g. cyclophosphamide (if necessary)
What is the pathophysiology of an aspergilloma?
Pre-existing cavity in lung parenchyma
Colonised by aspergillus, which forms ‘mycetoma within cavity’
Usually not invasive, but may produce erosion with haemoptysis
- due to oxalic acid released by hyphae
What are the risk factors for an aspergilloma?
previous cavitating disease
- old TB
- abscess
- bronchiectasis
- chronic intersitial lung disease
How do aspergillomas often present?
Often asymptomatic
Haemoptysis occurs in 50%
- recurrent
- sometimes life-threatening
Non-specific = weight loss, lethargy
Solitary mass on CXR
Fever and cough less common
What needs to be done to investigate an aspergilloma?
CXR = solitary pulmonary mass (classically)
- crescent of air around mass may be noticeable
Biopsy/fine needle aspiration
- pink necrotic centre, rim of active hyphae
Sputum - hyphae on cytology, culture
Bloods - aspergillus antibodies mildly raised
How should aspergillomas be treated?
Conservative if stable
- Anti-fungals are no good!!!
Surgical resection if troublesome bleeding
Bronchial artery embolisation if severe bleeding
Describe the pathophysiology of chronic necrotising pulmonary aspergillosis?
Occurs in those with mild-moderate immunosuppression
Aspergillus colonises bronchi/alveoli
- may invade locally
Th1/macrophage dominated immune response not able to clear infection => granulomas => necrosis and cavitation
