Respiratory Fungal Infections PDF

Respiratory diseases caused by fungi Prof.Dr.Ahmed Hussein Jasim The majority of fungi encountered by humans are harmless saprophytes but in certain circumstances ,some species may cause disease by infecting human tissue, promoting damaging allergic reactions or producing toxin...

Respiratory diseases caused by fungi Prof.Dr.Ahmed Hussein Jasim The majority of fungi encountered by humans are harmless saprophytes but in certain circumstances ,some species may cause disease by infecting human tissue, promoting damaging allergic reactions or producing toxins. Mycosis’ is the term applied to disease caused by fungal infection. Allergic bronchopulmonary aspergillosis Allergic bronchopulmonary aspergillosis (ABPA) occurs as a result of a hypersensitivity reaction to germinating fungal spores in the airway wall. The condition may complicate the course of asthma and cystic fibrosis , and is a recognised cause of pulmonary eosinophilia. The prevalence of ABPA is approximately 1%–2% in asthma and 5%–10% in patients with CF. A variety of human leucocyte antigens (HLAs) convey both an increased and a decreased risk of developing the condition, suggesting that genetic susceptibility is important.  Clinical features Common manifestations in the early phases include fever, breathlessness, cough productive of bronchial casts and worsening of asthmatic symptoms. The appearance of radiographic infiltrate may cause ABPA to be mistaken for pneumonia but the diagnosis may also be suggested by segmental or lobar collapse on chest X-rays of patients whose asthma symptoms are stable. Management ABPA is generally considered an indication for regular therapy with low dose oral glucocorticoids (prednisolone 7.5–10 mg/day) with the aim of suppressing the immunopathological responses and preventing progressive tissue damage. In some patients, itraconazole (400 mg/day) facilitates a reduction in oral glucocorticoids; a 4-month trial is usually recommended to assess its efficacy, but there needs to be consideration for the interactions with inhaled glucocorticoids. The use of specific anti-IgE monoclonal antibodies is under consideration Chronic pulmonary aspergillosis The term chronic pulmonary aspergillosis (CPA) encompasses simple aspergilloma, chronic cavitary pulmonary aspergillosis, chronic fibrosing pulmonary aspergillosis, Aspergillus nodule and semi-invasive aspergillosis. They are uncommon conditions and challenging to diagnose and treat. Simple aspergilloma Cavities left by diseases such as TB or by damaged bronchi provide favourable conditions in which inhaled Aspergillus may lodge and germinate. At the earliest stage, CT scanning may identify an irregular mucosal wall and, as fungal growth progresses, this finally collapses into the cavity, forming a fungal ball that may be identified on imaging  Simple aspergillomas are often asymptomatic. They can, however, give rise to a variety of non-specific symptoms, such as lethargy and weight loss, and may cause recurrent haemoptysis, which may be life-threatening. The typical radiological picture is invariably accompanied by elevated serum IgG/precipitins to A. fumigatus. Sputum microscopy typically demonstrates scanty hyphal fragments and is usually positive on culture. Less than half exhibit skin hypersensitivity to extracts of A. fumigatus. 1. Asymptomatic cases do not require treatment but haemoptysis should be controlled by surgery. 2. Tranexamic acid or bronchial artery embolisation may provide a bridge to surgery or palliate haemoptysis when surgery is not possible. 3. Antifungals can be trialled in those patients with multiple mycetomas or who are not fit enough for surgical resection. Instillation of antifungal agents, such as amphotericin B, via a catheter placed into the cavity has been reported but is rarely used in the UK. Invasive pulmonary aspergillosis Invasive pulmonary aspergillosis (IPA) is most commonly a complication of profound neutropenia caused by drugs (especially immunosuppressive agents) and/or disease Clinical features Acute IPA causes a severe necrotising pneumonia and must be considered in any immunocompromised patient who develops fever, new respiratory symptoms (particularly pleural pain or haemoptysis) or a pleural rub. Invasion of pulmonary vessels causes thrombosis and infarction, and systemic spread may occur to the brain, heart, kidneys and others organs. Tracheobronchial aspergillosis involvement is characterised by the formation of fungal plaques and ulceration.  HRCT characteristically shows macronodules (usually ≥ 1 cm), which may be surrounded by a ‘halo’ of intermediate attenuation if captured early (