Speaking about mycoses or dermatophytiases we indicate the mycoses of the skin structures and infections due to fungi of the stratum corneum, hairs and nails.
They are caused by fungi belonging to the genera:
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Tricophyton
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Microsporum
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Epidermophyton
The manifestations that occur depend on the type of infected structure and on
the inflammatory reaction of the infected organism towards the fungus or mycetes
(see also ringworms). To the side, an example of tinea barbae.
The gradual differentiation of the cells of the epidermis gives rise to the
stratum corneum and other keratinized structures
The epidermis and, therefore also the keratinized parts, are dynamic structures,
in the sense that the cells slowly move from the basal layer towards the
surface, differentiating into cells with keratin, which constitutes the hardest
layer of the skin, called the stratum corneum. To carry out this process it
takes time, usually a cell passes from the basal layer to the horny layer in 14
days.
Dermatophytes or fungi, if you prefer, are always present on the superficial skin, but the continuous peeling of the epidermis and the integrity of the hard skin layer, or stratum corneum, prevents the fungi from penetrating to the deeper layer of the skin, taking root to the skin and, therefore, infecting the organism. If this were the case, we would never have fungal infections, that is, if the skin were always intact and functional and covered with its natural defense represented by the cutaneous sebum, present both on the skin and on the hair, especially in the scalp. However, there are conditions that favor fungal infection.
Favorable conditions are represented by:
1) maceration of the skin, for example in the more "rubbed" areas, for example
under the armpits, in the groin, between the submammary folds where cutaneous
mycoses easily develop, especially from yeasts (cf. mycosis and candidiasis)
2) trauma and lesions of the skin layer
3) dry, parched, dehydrated skin
4) skin attacked with soaps that remove the skin's natural fatty acids
5) antibacterial therapies, by altering the organism's microflora
6) conditions of systemic defeat, eg. AIDS, tuberculosis, cachexia etc.
The dermatophytes penetrate, as we said, into the deepest stratum corneum
infecting it, only in this way does it happen
If the infection of the fungus that penetrates the skin layer does not generate
any immune reaction, the infection goes unnoticed, although this is a very rare
occurrence. More likely, however, fungal infection triggers an inflammatory
reaction directed against the causative agent which is mediated by lymphocytes.
The result is erythema and itching, sometimes the infection being so violent as
to cause the formation of vesicles. This inflammatory state is in turn
responsible for an increase in cellular mitosis which causes a thickening of the
stratum corneum itself, altering its natural shine, which is very evident in
nail mycosis. Macroscopically, the thickening of the stratum corneum and its de-epithelialization
are responsible for the characteristic appearance of cutaneous mycoses: whitish
areas, finely desquamated.
Generally the process lasts 3 to 4 months and is self-limited. Human infection
occurs through the reservoirs represented by animals (zoophilic fungi), eg. the
cat which in turn is affected by microsporum infections, or the soil itself (geophilic
fungi), eg. the gypseum, the m. fulvum, T. ajelloi. Most of the time, however,
infections become chronic either because the body is unable to defend itself or
because the doctor, in order to immediately relieve the infection, uses
cortisone, or local antifungal drugs associated with cortisone, or because the
subjects undergo therapies with immunosuppressive and antineoplastic drugs.
It seems simple, but it is not, if you take into account that a mycosis can be
super infected with pyogenic bacteria or because skin lesions, mistaken for
mycosis, are actually atopic dermatitis, i.e. forms of allergic dermatitis or
skin eczema or rosacea-like rashes. , or initial psoriatic lesions mistaken for
mycosis. The mycosis of the skin is characterized by the presence of redness
which is technically defined as "erythema", accompanied by desquamation and more
or less extensive vesicles.
These are well-demarcated, circular or oval lesions, accompanied by skin
pustules and nodules. The diagnosis can be confirmed microscopically by direct
detection of the hyphae, using potassium hydroxide. For the therapy of cutaneous
mycosis we use imidazole derivatives (clotrimazole>, econazole, ketoconazole,
miconazole and sulconazole) are all effective in case of ringworm. Terbinafine
cream is effective but more expensive.
Other topical antifungals include amorolfine, griseofulvin and undecylenates.
Topical athlete's foot preparations containing tolnaftate are over-the-counter
products. Antifungal powders have little therapeutic value for the treatment of
skin infections and can cause irritation; they can be used to prevent
reinfections. When using these drugs it is important to avoid contact with eyes
and mucous membranes and to take into account that they can cause local
irritation and hypersensitivity reactions including burning, erythema and
itching. If symptoms are severe, treatment should be discontinued. Their topical
use, that is local, is a treatment that must be protracted for a long time
before having the desired results, always after hearing the opinion of the
doctor who follows you. The palms of the hands or feet require prolonged therapy
up to 3-4 weeks. Once griseofulvin was widely used, especially in the most
extensive or nail lesions. Today it is used more rarely due to the significant
side effects on liver functions and gastrointestinal disorders. Systemic therapy
is often necessary for nail and scalp infections (see ringworm) or in cases
where the skin infection is extensive, disseminated or intractable. Adding
topical antifungal therapy can reduce the risk of transmission. The drugs used
are fluconazole and itraconazole, drugs to be used only under strict medical
supervision.