Aspergillus and Asthma

 

Aspergillus and Asthma

PKGhatak,MD

Aspergillum is a handheld holy water sprinkler used in church services. The spore forming fungus looks like a holy water sprinkler and the name is derived from there.

 Aspergillus is a mold that can lead to various human infections. Of the illnesses resulting from exposure to aspergillus, respiratory illnesses are common.  A certain group of people is more prone to fungal infection.

Aspergillus in sputum. 

 

 Aspergillum consists of many species of which Aspergillum fumigatus (A.fumigatus), A.niger, A.flavus, are important human pathogens. Aspergillum is a saprophytic spore forming warm weather fungus. It can be found in every organic decaying substance in the presence of moisture. Besides causing human diseases, enzymes obtained from aspergillus are used extensively in food industries. Citric acid is obtained from A.Ozoro and A. flabus is hated by farmers because it causes the spoiling of grains.

This fungus multiplies by spores. The spore can withstand a temperature of 70C. The filamentous form of the fungus is called hyphae and the mass of hyphae is called mycelia. Hyphae and mycelia are destroyed at higher temperatures. Aspergillum produces aflatoxin, which can cause liver cancer. The fungus is easily cultured in the Sabouraud medium. It grows in 5 days.

Aspergillus produces three groups of illnesses in humans. 1. Allergic, 2. Locally infective and 3. Invasive forms.

 In nature, the Aspergillus spore is everywhere and also in the air we breathe. The spores are harmless to humans except those who are susceptible for the following reasons.  Asthmatics, Cystic Fibrosis, chronic corticosteroids users, taking immunosuppressing medications, bone marrow transplants and solid organ transplants, people with low white cell count (WBC) and cavitary lung diseases.

Wound infection with aspergillus has been a serious problem, particularly following Coronary Graft operations. Less frequently localized infections like that of eyes, nasal sinuses, inner ear, pleura, pericardium, and skin are seen. 

Invasive aspergillosis is generally a very serious disease. It is feared in bone marrow transplantation.

Diagnosis of Aspergillosis.

 In lung diseases.

Identification of aspergillus in sputum stained and observed under the microscope is the most direct way to identify it. Cultures are performed for confirmation. Identifying the fungus in tissues requires a biopsy. Identification of fungus from blood and bodily secretions may not be easy, but cultures are positive. For the invasive lesions, a positive test for the fugal antigens Beta d- glucan and Galactomannan is generally available.

In allergic aspergillosis.

Blood eosinophilia and elevated IgE levels are common, but the tests are non-specific. IgE precipitin test against aspergillus antigen is often positive. A standard skin test is an alternative diagnostic test.

Asthma.

In asthma, airway inflammation is often due to allergies to common house dust, tree and weed pollen, shellfish, animal dandruff, cockroaches and allergy to drugs- specially to the penicillin group. And about 12% are due to hypersensitivity to Aspergillus.

Asthmatics are susceptible to repeated infections and asthma becomes chronic aspergillus spores find a foothold in the small airways.

Worsening of asthma which does not respond to medication, is likely from aspergilla infection. Mucus plugs that are coughed up are loaded with eosinophils and back-brown materials. The brown-black material is the mycelia of aspergillum.

Repeated bouts of aspergillus infection are the rule. Eventually, weakness of bronchial walls produces small areas of bronchiectasis and that produces hemoptysis.  On x-ray, these bronchiectatic areas appear as finger shaped shadows. Usually seen in smaller airways in the central areas of the upper lobes.

Bronchopulmonary aspergillosis.

As the aspergillus began to spread out from the bronchus to the parenchymal of the lung, it takes several clinical pictures as follows-

 1. Nodular lesions – one or more in number. Pathologically these are granulomas.

 2. Pulmonary fibrosis – repeated bouts of infection produce scarring of the lungs.

 3. Cavitary lesions with fungus ball formation are called mycetoma. Mycetoma is more often seen secondary to preexisting cavities of the lungs as in Tubercular cavitary disease, emphysema, and sarcoidosis.

4. Invasion of blood vessels and distant spread.

Aspergilla infection or hypersensitivity disease in asthma are important causes of exacerbation of asthma. In chronic asthmatics, aspergillosis can take several clinical courses. Prompt identification of the fungus and proper fungicidal medication should be prescribed early and in addition to other asthma drugs.

****************************************************************