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On a CT scan, the ‘air crescent’ is strongly suggestive of a fungal infection.

Lungs normally look black on a CT scan because they are full of air, with the ribs around them appearing bright white because bone is much denser.

In invasive aspergillosis, the growing nodule may at first show up with a fuzzy white ‘halo’ made up of microscopic bleeds. A couple of weeks later, the dying lung tissue shrinks down into a firm ball, leaving an air-filled gap that looks like a crescent moon on a CT scan.

Non-invasive fungal balls that grow in pre-existing cavities (e.g. following tuberculosis) also produce an air crescent, but in this case the entire ball is made up of a dense mass of fungal strands, mucus and cell debris.

 Read more about air crescent (also known as Monad sign).

Spores are the fungal equivalent of seeds: tiny dormant packages that are tough enough to survive in the environment until they find a new place to grow. Like seeds, they germinate and grow shoots (hyphae). This picture shows a scanning electron micrograph of germinating Aspergillus fumigatus spores (provided by KM Lord and ND Read). In this picture the spores are clustered in the middle, with the germ tubes (first growing shoots) radiating outwards.

Aspergillus spores are so tiny they look like fine black dust. We all inhale hundreds every day, but in healthy people they are cleared away before they have the chance to germinate by white blood cells or by tiny hairs (cilia) that physically sweep them out of the lungs.

People who have immune deficiencies (e.g. leukaemia, AIDS, transplant recipients) or carry certain genes are unable to stop the spores from growing. Aspergillus is particularly suited to growing in the crevices formed by lung damage caused by other lung conditions (e.g. COPD) or an old infection such as tuberculosis. Eventually, the strands of fungi (hyphae) grow to form a tangled mass (mycelium) mixed in with mucus and general debris. If the resulting fungal ball is very well localised it may be possible to surgically remove that part of the lung, or the ball may be coughed up.

Aspergillus can punch through the lining of the lungs and invade the blood vessels below, in a process called angioinvasion. It can result in blockage (occlusion) of the blood vessel and damage to the local tissue through lack of oxygen (infarction). In severely immunocompromised patients, fragments can even break off and travel to other organs in the body.

In this image, a tissue section through a blocked blood vessel has been stained with the dyes haematoxylin (purple, binds DNA) and eosin (pink, binds proteins). The circle is the wall of the blood vessel – it is completely blocked with fungus.

·         Read more about Aspergillus angioinvasion

·         Read more about H&E staining

During a CT-guided needle biopsy, a radiologist may use an X-ray or CT scanner to guide a hollow needle between the patient’s ribs to retrieve a tissue sample from the lung. Part of the sample will be fixed in formalin and examined under a microscope, while the other part will be tested microbiologically to see whether any fungi can be grown from it.

In this picture, the patient is lying on their front with the needle going into their back to take a sample from the large inflammatory (whitish) area of the lung. Both lungs show considerable destruction of normal architecture, typical of emphysema, indicating that the patient was a heavy smoker.

Needle biopsy is less invasive than surgical biopsy, and will normally not require general anaesthesia: patients would usually receive local anaesthetic and sometimes another medication to relax them. They may need to avoid eating or taking certain medications (particularly blood thinners) some time before the procedure. The biopsy will generally take under an hour.

·         Read more at RadiologyInfo.org

When two German tourists found a body frozen in the ice on a ridge in the Alps, they assumed it was a mountaineer and reported it to the police, but an axe frozen alongside him revealed him to in fact be around 5,300 years old.

Ötzi the Tyrolean Iceman is Europe’s oldest known natural mummy. Different causes of death have been debated over the years, including bleeding to death from an arrow wound or being overtaken by a snowstorm. He may have been weakened by hunger, recent illnesses and infestation with parasitic whipworms.

On top of those problems, DNA from Aspergillus (probably fumigatus) was detected in his lungs by Dr Cano of California Polytechnic State University. But it is unclear whether the fungus was causing disease or from post-mortem contamination.

·         Read more at NY Times

·         Read more about Ötzi on Wikipedia

·         Read more about fungi causing biodeterioration of mummified Capuchin monks and ancient parchments