Pityriasis versicolor (also known as bran lichen, bran fungus lichen) is a fungal infection of the uppermost skin layer, which is conspicuous by spots distributed over the entire body, which appear lighter in color compared to the rest of the skin. The cause of this disease is the yeast fungus Malassezia furfur (formerly also called Pityrosporum ovale or Pityrosporum orbiculare). This fungus is found on the surface of the skin in almost every person, especially on the scalp, but usually without causing symptoms.
Why the fungus leads however with some to an illness and with others not, is not finally clarified until today. It is known, however, that there are some factors that favour a pathological (diseased) development. These include the summer months (with humid, warm climate and high UV radiation), increased sweating and certain basic diseases (for example diabetes mellitus or thyroid diseases).
In addition, pityriasis versicolor, like almost all fungal infections, is more likely to manifest itself in people in whom the immune system is weakened for some reason (for example, as a result of taking certain drugs or in the case of diseases that suppress the immune system, such as AIDS). The main symptom of bran fungus lichen is the white patches (hypopigmentation) on the skin. Depending on the type of infestation, these spots are small and occur only sporadically, especially in sweat-exposed areas such as the forehead or back, or they are larger and can “flow together”.
This results in a marbled skin appearance, which is often described as “map-like”. These discolorations are caused by the fact that the fungus spreads over a large area of the skin. It produces a toxin that inhibits the production of the pigment melanin, which is responsible for tanning the skin.
In addition, the affected areas are not exposed to sunlight as much as the rest of the skin, because they are covered by the fungal turf. Therefore, when patients are exposed to the sun, they tan on all parts of their bodies except those on which the fungus is present. In some cases the skin changes may itch a little, but not very much.
If affected persons scratch themselves, this can also cause superficial flaking of the skin. Pityriasis versicolor is not painful, and it is harmless and not contagious. The diagnosis of pityriasis versiocolor is usually a diagnosis of the eye, at least for an experienced dermatologist, due to its characteristic appearance.
In some cases it is useful to use a special examination lamp that emits black light to examine the skin. Important for differentiation from other skin diseases are the only slight itching, if any, and the typical infestation pattern of areas with a particularly large number of sweat glands. If necessary, the doctor can confirm his suspicion with the help of a light microscope.
To do this, he must scrape off and stain some skin scales, which are then placed under the microscope. There, the fungal cells appear as clustered bunch-like spheres. The therapy of pityriasis versicolor can be local or systemic.
Usually a local treatment is started. Various anti-fungal agents (antimycotics) can be used for this. Clotrimazole, bifonazole, econazole or naftifin are frequently used.
These are usually used in the form of an ointment or cream, but there are also hair shampoos, washing gels or sprays containing these active ingredients. In more severe and therapy-resistant cases a therapy with tablets should be used. These contain either Fluconazole, Ketoconazole or Itraconazole and are only available on prescription.
After a treatment, it can sometimes take some time for the skin to regain an even pigmentation although the fungal infection has been eliminated. Frequently, even after successful treatment, a recurring disease (relapse) occurs. In patients who have a tendency to recurrent pityriasis versicolor, it may be considered whether it is advisable to regularly use locally acting antimycotics (e.g. as shampoo with selenium disulfide).
