Dermatophytes are mycoses of the dermis caused by dermatophytes a type of ascomycetes (a class of fungi whose reproduction occurs by ascospores) that is distinct from yeasts such as candida or other fungi that cause superficial mycoses.
Dermatophytes are able to attack epidermal, nail, or pilar horny structures by keratin breakdown through enzymatic activity. The products of the activity of the degradative enzymes, are then nutrients for dermatophytes.
They are therefore known as keratinophilic fungi, restricted to the stratum corneum of the epidermis because of their inability to invade the viable tissue of an immunocompetent.
They have "virulence" factors such as acid proteinases, keratinases, and other proteinases.
Just to highlight the difference with yeasts (candida), the latter affect the periungual tissue, corners of the mouth, ano-genital area and folds.
Not being endowed, as is the case with the entire dermatophyte community, with keratinase enzymes, they are unable to invade intact horny tissue.
So they are only able to penetrate through a damaged stratum corneum, which explains their affinity for body districts with maceration and trauma.
Yeasts (candida) are also referred to as opportunists; in fact, they switch from the role of a simple commensal to an infectious one under certain favorable situations: moisture, maceration, antibiotics for a long time, pregnancy and immunological deficits (HIV).
It is estimated that in 2010, fungal infections (dermatophytes and yeasts) of the skin were the fourth common disease in the world affecting around 900 million people.
A little history
.We find the first references to mycoses and more specifically ringworm in "De Morbis Cutaneis" (1572) by Gerolamo Mercuriale, a physician born in Forli in 1530. The volume, the first treatise on dermatology, is composed of oral lectures collected in two books by Mercuriale's student Paolo Aicardi.
Even earlier Gerolamo Fracastoro in 1546 in "De Contagione et Contagiosis Morbis" describes tiny particles called "seminaria" transmissible from one subject to another by air, by objects or by direct contact. It also brings attention to Ringworm and the seminaria that causes it, which are "crassiora" (coarse) in nature as opposed to internal diseases that are "subtiliora" in nature.
Dermatophytes have throughout history been the subject of discoveries, descriptions and classifications but also of careful clinical study.
Between the fathers of skin microbiology, the Hungarian David Gruby, studied this subject in 1800. In an 1843 memoir he described Microsporum Audouini and cases of tonsuring ringworm (from the symptomatology), mistaken by the scientist for Celsian Ringworm (also called Porrigo Decalvans)
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This mistake ensured that Microsporum was officially recognized with a 50-year delay, rediscovered in 1892 by physician Raymond Sabouraud (1864-1938).
He was appointed director in charge of the Tigne Laboratory at Saint Louis Hospital in Paris and was then distinguished for studies on tigne and other skin mycoses.
Other important studies were conducted by the Viennese school of dermatology, founded by Ferdinand Hebra, born in Brno, Moravia (1816-1880), a worthy pupil of anatomopathologist Karl Rokitansky and clinician Jaoseph Skoda. Hebra described the eczema marginata that bears his name, also called tinea inguinale.
Other hospital centers specifically for the treatment of tinea and other mycoses include the San Gallicano in Rome, founded in 1720 by Pope Benedict XIII (1649-1720), from the beginning set up and prepared to deal with tinea, lue and scabies.
Symptoms and diagnosis
The dermatophytes that generate dermatophytes are divided into three genera: Microsporum, Trichophyton and Epidermophyton. Infection with these mycetes is called Tinea and is characterized by symptoms such as rash, itching and scaling. They are identified as:
- Tinea capitis (scalp)
It can be identified objectively when alopecic patch(s) are present with truncated hairs at the follicular outlet, always appears finely scaling. The skin is more inflamed in the affected scalp area when Trichophyton are involved than Microsporum particularly canis.
Tinea capitis, a special form of Tinea capitis and is determined by Trichophyton Schoenleini.
It gives rise to definitive scarring alopecia and is characterized by yellow, inverted bowl-shaped lesions with an odor ranging from sulfur to urine and with broken hair inside.
- Tinea Corporis (body)
Generally minimal or absent inflammation, mildly itchy patches with person-to-person, animal-to-person transmission, rarer from soil to person.
The patches e.g. on face, trunk and limbs, are pink to red annular, the edges flaky with slight detection, tendency to expand toward the periphery and clear in the central area.
- Tinea Cruris or Eczema marginalis of Hebra (groin)
(Hebra's marginal eczema) is the form of inguinal tinea from Epidermophyton Floccosum.
Generally broad red/brown or light brown plaques with well-demarcated raised margins that flake producing itching.
The plaques are usually located on both sides, from the groin to the thighs, even extending sometimes to the crease between the buttocks to the scrotum.
The mycetes are favored in their development by maceration, heat, and moisture.
- Tinia pedis (Also called athlete's foot)
From Trichophyton Rubrum produces desquamation and plantar thickening with typical moccasin-like distribution. It manifests with skin redness, scaling, hyperkeratosis, nail thickening, and itching. It gives off a foul odor and may present with skin cracking. Contagion normally occurs through contact with the soil, in wet places or in swimming pools.
Also responsible for Tinia Pedia are Epidermophyton Floccosum and Trichophyton Mentagrophytes interdigitalis variant.
- Tinea Unguinum (nail) .
It can affect both fingers and toes.
It causes increased thickness of the nails, which are white/yellowish in color (dyschromic patches). Subsequent to thickening they become brittle and rough, easily deformed or broken.
It can also affect the nail plate, nail bed or both areas, keratin and debris accumulate under the nail and in any case distally (the nail can also become dislodged from the bed). The dermatophyte responsible is mainly Trichophyton Rubrum, but often non-dermatophytic molds, Aspergillus or Fusarium, are also responsible.
Therapy
The typical antifungal treatment is clotrimazole, fluconazole, ketoconazole, cyclopiroxolamine, thioconazole.
When the infection is resistant to common treatments, systemic antifungals (particularly used then directly in Tinea Capitis and Tinea Unguinum) are envisioned, among which certainly emerge traconazole, terbinafine, and also fluconazole tablets.
We always remember that Tinea is extremely contagious, and is spread through contaminated objects (clothing or bathroom furnishings) but particularly through contact with people or pets.
The infection can then spread to other parts of the body. That is why it is very important for our relationship with others but also for ourselves to start antifungal therapy as soon as possible with targeted drugs aimed at neutralizing dermatophytes.
They are also used to prevent the spread of the infection.
To support this, acid ph antifungal cleansers and sprays are then also used to make the treated skin refractory to "fungal invasions" also based on phytotherapeutic compounds (Teatreeoil for example) but also more chemical type such as undecylenic acid (fatty acid derived from castor oil).
Remember that sweating, humidity, and maceration are a formidable habitat for dermatophytes.
For diagnosis normally a thorough objective examination is sufficient but often a skin sample is useful to observe under a microscope.
So for purely preventive purposes we can recommend before leaving to use personal towels and combs, do not go barefoot and if possible always use socks, avoid contact with animals or people suspected of fungal infections.
After taking a shower or bath (pool-sea) dry the skin thoroughly, change clothing often especially undergarments if you tend to sweat excessively by avoiding excessively hot environments.
In case of intense skin secretion, use talcum powder or topical products with anti-sweating action (e.g., aluminum chloride) and especially in the folds (submammary furrow, armpits, groin, intergluteal furrow, feet and hands).
Traveling
Dermatophthias are infections that occur more often in hot and humid climate environments such as tropical climates. So if you notice patches, round or oval, mildly itchy, scaling and raised irritations, a less pronounced color center when you return from exotic vacations, you should be seen by a dermatologist, preferably in a tropical dermatology center.
When collecting anamnestic data, it will certainly be interesting to mention whether you have touched animals of the dog and cat type, whether you have frequented swimming pools and barefoot locker rooms, or otherwise the type of climate of the resort where you have vacationed.
BBibliography
.Medical Psychology Illustrated, Antonio Luigi Costa Arti Poligrafiche Europee.
Atlas of Mycology, A. Lasagni Universe
.The fungal infections of the foot, Marseglia Morato Piccin Edizioni
Testa Dermatology and Venereology, Delfino-Fabbrocini-Balato Idelson-Gnocchi.
The Dermatophthias, various authors Piccin Editions
.Manual of Medical Mycology, V. Vidotto Masson Editions.
