Malassezia Furfur: Infection, Transmission & Diseases

Malassezia furfur is a yeast fungus that occurs in the natural skin flora of almost everyone. The microorganism does not normally harm its host, but in some circumstances it can multiply greatly and then causes inflammatory reactions of the skin, such as redness and scaling, which in certain cases are paired with itching.

What is Malassezia furfur?

Malassezia furfur belongs to the yeast family. These are single-celled fungi that develop energy from the breakdown of organic matter. The fungus is characterized by an oval, cylindrical or round cell structure and belongs to the class of fungi imperfecti. These so-called imperfect fungi refer to tubular, upright or yoke fungi that reproduce by forming spores. The name of Malassezia furfur is composed of Malassezia (after Louis-Charles Malassez, a French physician and bacteriologist from the 19th century) and the Latin term furfur for “skin scab”. Malassezia furfur occurs mainly in humans, but has also been found in other living creatures, for example, dogs.

Occurrence, distribution, and characteristics

The protozoa range in size from 1.5 to 5.5 µm and consist of round or oval fungal cells that reproduce by asexual spores. The fungus is thought to be present in the skin flora of over 90 percent of all people. Transmission and spread occur unnoticed. Direct skin contact is not necessary; contact with contaminated bath mats, clothing or shoes is sufficient. Passing on from person to animal is also possible. Malassezia furfur has lipophilic properties, which means that it can dissolve fats and oils particularly well. The skin fungus feeds on sebum, which is produced in the human skin and consists of long-chain fatty acids. It is therefore particularly common in skin regions where sebum is increasingly produced, for example on the hairy scalp, on the face or on the chest and back. Since the onset of puberty is also accompanied by increased sebum production, an increased colonization with Malassezia yeasts can be observed for this stage of life. In old age, the sebaceous gland function and thus the colonization density decrease again. Extreme proliferation of the fungi and thus skin disease occurs only in certain individuals who are susceptible to it, and then also repeatedly. As favoring factors for the excessive multiplication a damp-warm climate is considered. Thus, in tropical regions almost every second person is affected, in the temperate zone only one percent of the population. An immune system weakened by infections or diseases is also considered a risk factor for excessive colonization with Malassezia yeasts.

Diseases and ailments

If the fungus multiplies too much, it overgrows the other microorganisms of the skin flora. A fungal infection develops, causing scaly, sharply demarcated patches. Since the fungus can absorb UV radiation, the skin’s melanin production is not stimulated under the fungus, which prevents these spots from tanning when exposed to sunlight. These skin changes can become progressively larger and occupy entire skin areas. Depending on the manifestation, different forms are distinguished. In the case of pityriasis versicolor, the most common superficial mycosis, the sharply demarcated, yellowish-brown and scaly areas form mainly on the chest and back. These may spread to the lateral trunk as the infestation progresses. The clover-shaped scaling can be easily scraped off with a wooden spatula. If long-lasting pigmentary disorders remain after these spots have healed, the condition is referred to as pityriasis versicolor alba. Another manifestation is seborrheic dermatitis, which is manifested by whitish-yellowish and greasy skin scales that occur especially on the scalp and face. The skin under the dandruff is reddened due to inflammation. Eyebrows and the beard area are also often affected. In most cases, however, these skin changes in the form of redness are perceived by those affected merely as a cosmetic impairment, as they rarely cause discomfort such as itching or burning. In contrast, Malassezia folliculitis, which is characterized by small, highly itchy papules and pustules, occurs comparatively rarely.Here, the fungal infection is no longer merely superficial, but the yeast bacteria have penetrated into deeper layers, where they lead to the aforementioned inflammatory reactions. Mycosis can be diagnosed by a dermatologist using a so-called radio allergen sorbent test (RAST), in which specific immunoglobulins against allergens are detected in the blood. However, since this examination method is comparatively expensive, a sample of the scales is usually taken instead by tearing off scotch tape and examined under the microscope. Since fungal infections do not heal on their own, medical treatment is necessary. For this purpose, the physician prescribes antimycotics in the form of ointments, gels, shampoos or creams. Fungal infections are stubborn, so it is not recommended to stop the therapy too early. Furthermore, care should be taken to thoroughly disinfect contaminated clothing to prevent reinfection. Fungal skin infections are usually harmless. In exceptional cases, there is a risk of systemic mycosis. In this case, the fungus not only colonizes the skin, but also reaches the organs via the bloodstream. This represents a first serious disease, which can be very dangerous, especially for immunocompromised persons, and in the very worst case leads to death.