Fungal Infections

Pneumocystis Jirovecci

This is a fungal infection that is seen in immunocompromised patients.

It is an AIDS-defining disease, typically causing a pneumonia in HIV positive patients.

Symptoms

Atypical pneumonia (SOB, dry cough, fever) but very few chest signs

The classic symptom is desaturation of SpO2 during exercise/exertion

Can lead to secondary pneumothorax, hepatosplenomegaly and lymphadenopathy

Key tests

Blood tests show raised inflammatory markers and fungal markers (beta-glucan)

CXR/HRCT shows bilateral interstitial pulmonary opacifications

Sputum culture – this can be taken directly or from bronchoalveolar lavage if needed

Lung biopsy may be required if diagnostic doubt

Management

Co-trimoxazole is used first line. If not suitable, can use pentamidine

Co-trimoxazole prophylaxis is recommended in immunocompromised patients, e.g., HIV patients with CD4 count < 200/mm3 and post-transplant patients 

Cryptococcus Neoformans

This is a yeast found in bird droppings which can infect the central nervous system.

It is a systemic opportunist which typically causes infections in immunocompromised patients as well as IV drug users.

A classic presentation is meningitis in AIDS patients with CD4 count < 100 cells/mm3

Symptoms

Meningitis (fever, headache, seizure, vomiting)

Focal neurological deficit

Key tests

CT head shows circular lesions and cerebral oedema

Lumbar puncture – CSF has high opening pressure, India ink test positive

CSF shows raised lymphocytes, low neutrophils, raised protein, low glucose

Management

Antifungals e.g., amphotericin and flucytosine

Aspergillus Fumigatus

This is a mould which affects the lungs both directly and indirectly.

It is a systemic opportunist and so typically affects those who are immunocompromised or more susceptible to infection.

It can contribute to the development of illnesses like asthma and Extrinsic Allergic Alveolitis

However, in immunocompromised people, it can also cause direct pathologies:

Allergic Bronchopulmonary Aspergillosis (ABPA)

Aspergillus fumigatus causes type I and III hypersensitivity reactions and is particularly seen in people with asthma and cystic fibrosis.

The hypersensitivity reactions cause bronchoconstriction (giving asthma symptoms) and potentially even permanent damage (causing bronchiectasis).

Symptoms

Wheeze and Dyspnoea

Cough with sputum containing fungal hyphae

Bronchiectasis

Recurrent chest infections

Key tests

Blood tests show raised fungal markers, IgE, beta-d-glucan and IgG precipitins

High resolution CT shows bronchiectasis

Radioallergosorbent (RAST) aspergillus test

Management

Steroids are first line.

If poor response, antifungals (e.g., itraconazole) can be added 

Aspergilloma

This is when the mould forms a fungal clump within a body cavity.

It is seen more in patients who have pre-existing lung cavities, secondary to conditions like TB, sarcoidosis or lung cancer.

Risk factors

TB

Sarcoidosis

Lung cancer

Symptoms

Asymptomatic in most people, however can resemble a lung cancer

Cough with blood, weight loss

Key tests

CXR shows lung cavity

Bloods show high titres of IgG Aspergillus Precipitins

CT shows air-crescent sign

Management

Antifungals (itraconazole, amphotericin), consider surgical excision

Invasive Aspergillosis

This occurs in people with a severe neutrophil deficiency.

The mould becomes invasive and starts to penetrate the lungs and paranasal sinuses and has a high mortality.

Risk factors

HIV

Leukhaemia

Immunosuppression

Key tests

Made by a lung biopsy     

Management

Antifungals e.g. IV Voriconazole and Amphotericin