Skin Fungi - Cutaneous Mycoses

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and of the dermis, generically known as cutaneous mycosis (or dermatomycosis)

Skin Fungi - Pityriasis Versicolor

Also called mycetes, fungi are commonly present in the skin flora and in the environment, but generally do not pose a problem; in fact, they tend to "coexist" with the human organism in the saprophytic state, without causing harm. All this thanks to several defensive factors that protect the human body from their excessive development.
In some favorable conditions, however, cutaneous fungi can turn into invasive pathogens, behaving like opportunistic microorganisms. In practice, these fungi are capable of “exploiting” a weakened immune state of the organism to increase their colonies on the skin, to the point of causing disease.

Not surprisingly, infections caused by skin fungi are found more frequently during the summer, when the heat and humidity typical of the summer season facilitate their growth and spread among individuals (given the frequentation of crowded places, such as swimming pools and beaches).
The symptoms associated with mycosis of the skin manifest themselves in the skin sites and in the attached structures (eg scalp, nails, genitals or skin surface) that they infect.

Epidemiology varies from one form of mycosis to another and is largely influenced by multiple environmental and subjective factors.
The diagnosis is based on the clinical appearance of the lesions, detected at the dermatological examination, and on the microscopic and cultural examination of the infected tissue.

Treatment depends on the site of infection, but generally involves the use of topical or oral antifungals, aimed specifically at the skin fungus in question.

of plants or animals. Mycology experts are able to identify and classify fungi based on their microscopic appearance and method of reproduction, which can occur both sexually and asexually. The fungi that infect human skin are microscopic in size and can be single-celled with an ovoid shape (like yeasts) or multicellular and filamentous (like molds).
  • The pathogenic species for humans can cause mycosis, poisoning or allergies. Diseases attributable to their presence can also be systemic, ie they can involve the internal organs of the human body (an example is aspergillosis, which affects the lungs), but the topical forms, ie localized on the skin, are far more frequent. Generally, cutaneous mycoses are superficial and caused by dermatophytes or yeasts.
  • Fungi are transmitted very easily and can overcome the resistance of the human body's barriers, settling into the skin. Almost all pathogenic species behave as opportunists, therefore they are able to take over in situations of immunosuppression (prolonged or frequent antibiotic therapies, use of cortisone drugs, chemotherapy, etc.). Furthermore, skin fungi proliferate in the presence of hot temperatures, high humidity, excess and stagnation of sweating, poor hygiene and changes in skin pH.
  • : they are a particular type of pathogenic microorganisms that infect the superficial skin layers (stratum corneum of the epidermis) and the keratinized annexes (hair, hair and nails), sites in which the presence of keratin (a protein rich in sulfur) is abundant. which they feed on.
    Species belong to this category Epidermophyton, Microsporum And Trichophyton.
    Dermatophytes are responsible for characteristic rosette-shaped, sharp-edged skin macules with centrifugal evolution (ringworm). Some of these fungi can infect the trunk (tinea corporis), feet (tinea pedis or athlete's foot), nails (tinea unguium) and inguinal folds (tinea cruris). These infections make up about 40-50% of all. superficial mycoses and differ from candidiasis in that they are only rarely invasive.

    Skin Fungi - Tinea Pedis (Athlete's Foot)

    • Yeasts: they are single-celled and non-filamentous microorganisms that reproduce very quickly in an asexual way, localizing in warm-humid areas of the body (oral cavity, armpits, submammary folds, interdigital spaces, anogenital region, etc.).
      Many yeasts are normally present on the skin and do not cause damage (they almost always coexist in a saprophytic state).
      The most important yeasts in dermatology are: Candida albicans, Malassezia furfur And Cryptococcus neoformans.
      Depending on the fungal agent responsible and the affected area of ​​the body, visible skin manifestations may include edema, redness and pinkish-white desquamative patches; itching is almost always present.
    • Molds: are multicellular and filamentous fungi that reproduce sexually.
      The most common pathogenic molds are: Alternaria, Aspergillus And Fusarium. These types of fungi are mainly responsible for deep and systemic mycoses, while only in rare cases they cause skin and superficial infections.
    In general, these pathologies can be divided into two types:

    • Superficial and cutaneous: limited to the superficial layer of the skin (epidermis), hair, nails and mucous membranes (oral cavity and genitals);
    • Subcutaneous: extended to the dermis and connected structures.

    Skin diseases due to fungi can affect everyone, regardless of gender and age. In most cases, people who develop cutaneous mycosis have a reduced immune response, for example due to an "alteration of local defenses (eg trauma with vascular compromise) or" immunosuppression (eg diabetes, AIDS, antibiotic dysbiosis, etc.).
    Transmission can occur from person to person, from animal (cat, dog, rabbit, mouse and cattle) to person and, rarely, from contaminated soil and objects to humans.
    The most frequent fungal infections of the skin are:

    • Dermatophytosis: Fungal infections involving keratinized areas of the body (stratum corneum, hair or nails). Symptoms can vary, but most of the time they are skin lesions, which rarely itch.
    • Candidiasis: mycoses that mainly affect sweating areas, such as groin, armpits and interdigital areas. At the level of the mucous membranes, the oral cavity (e.g. thrush), the genitals (e.g. vulvovaginitis from Candida albicans) and the esophagus (especially in immunosuppressed subjects).
    • Pityriasis versicolor: fungal skin infection in which small, flat, uneven patches appear on the neck, trunk, abdomen, arms and face.
      Characteristic of the disease is the alteration of skin pigmentation (dyschromia): the lesions are hypo- or hyper-pigmented and take on a color ranging from white to brown. The colonized skin areas, in fact, if exposed to the sun, hinder the passage of ultraviolet rays which, in normal conditions, stimulate the production of melanin.
    to react to infections.
    These conditions include:

    • Wrong eating habits;
    • Insufficient hygiene;
    • Physical stress;
    • Hot and excessive humidity;
    • Situations of chronic skin maceration (excessive sweating, habit of wearing poorly breathable clothing);
    • Prolonged antibiotic or cortisone-based therapies;
    • Immune defense compromised by particular pathologies (AIDS, tumors, diabetes, etc.);
    • Taking immunosuppressive drugs.
    or slightly itchy, with a peeling and slightly raised edge.

    In some fungal infections, the lesions are whitish first, then tend to darken over time.
    Most of the time, the inflammation is little or no, but occasionally when the inflammation is more severe it involves damage to the structures involved, manifesting as a sudden blistering or bullous disease (usually in the feet) or as a "large soft lesion of the scalp that results in areas of alopecia (kerion).
    Other symptoms associated with skin fungus include a burning sensation, sudden onset blisters and cracks (especially in the feet), thickening of the nails and dandruff-like scaling of the scalp.

    it can take biological material (scales, hairs, hairs or nail fragments), by means of scarifications or tampons, from the site of the mycosis, and then observe it under a microscope or submit it to culture examination.
    For the differential diagnosis, the doctor can also use the Wood's lamp, able to detect a typical fluorescence (e.g. golden yellow of the Malassezia, greenish for dermatophytes, etc.) and exclude these dermatosis infections not caused by fungi.
    Once the type of skin fungus responsible for the clinical symptoms has been identified (through culture), the doctor can prescribe a specific therapy.

    topicals (such as hydrocortisone). Oral corticosteroid drugs are rarely used to treat severe inflammatory lesions.

    For further information: Drugs for the treatment of mycosis of the skin », modify the pH of the skin and favor the stagnation of humidity.

  • Choose the right cleansers to maintain the skin's defensive properties against fungi (eg eudermic cleansing bases instead of soap) and dry well after showering.
  • Do not abuse the drugs: antibiotics and corticosteroids should be taken only on medical advice and for a limited time, as they can weaken the immune system and favor the attack of microorganisms, such as skin fungi.
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