Dermatophyte mycosis of nails – appearance, causes, treatment

Proven content

Dermatophytosis of the nails is an infection of the nails caused by dermatophytes, causing subungual keratosis with loss of transparency and discoloration of the nail plate, and characterized by simultaneous involvement of the nail plates, the presence of symptoms of transverse and twig nets in some cases, and no inflammation of the periungual tissue.

What causes nail dermatophytosis?

In principle, all pathogenic dermatophytes for humans can cause dermatophytosis of nails, although some of them are found in nails quite exceptionally. More than 99% of onychomycoses are caused by dermatophytes. Currently, the most frequently isolated nail dermatophytes are:

1. Trichophyton rubrum, found in about 70% of cases,
2. Trichophyton mentagrophytes occurs in over 20% of patients with dermatophytosis of the nails.
3. less often Trichophyton tonsurans,
4. quite occasionally Epidermophyton floccosum.

Dermatophytosis of the nails occurs mainly in adults. Rare occurrence nail dermatophyte infections in young children is associated with the rapid growth of the nail plates, which prevents the development of infection, as the fungus is eliminated from the rapidly growing plate. Most often, however, dermatophyte mycosis of the nails occurs in elderly people, which is associated with a very slow growth of nail plates and a much more common impaired blood supply in the limbs in older people.

The following factors also predispose to the development of nail dermatophyte infection:

1. cellular immunity disorders associated with immunosuppression in the course of concomitant disease (eg AIDS) or caused by the treatment, as well as hormonal disorders occurring in diabetes, Cushing’s syndrome or hypothyroidism.
2. environmental and occupational factors (hence dermatophyte infections of the nails are more common among people staying in boarding houses and barracks, as well as in sportsmen and miners).

DIG. G-6. Nail fungus.

DIG. G-7. Nail fungus.

DIG. G-8. Onychomycosis – distal and lateral sub-plaque form.

DIG. G-9. Onychomycosis – distal and lateral sub-plaque form.

The mechanism of dermatophyte mycosis of the nails

Dermatofity by enzymatic means they mainly break down young soft keratin and therefore they develop most abundantly in the part of the plate adjacent to the nail bed (placental layer) and closer to the nail root. The growth of dermatophytes in the plate itself is clearly determined by its cell structure. The fungus threads penetrate between the nail cells, because the intercellular substance resists the fungus less than the cytoplasmic keratin, and hence the fairly regular course of the fungus threads corresponds to the cellular structure of the nail.

Growing in the placental layer of the plate, some of the dermatophyte hyphae move towards the nail root, usually faster than the plate itself, growing back in the opposite direction. Most fungal hyphae maintain a predominantly transverse growth direction associated with lamellar structure of the nail. As a result of the enzymatic decomposition of keratin, gas-filled channels are formed next to each other, at the bottom of which there are fragments of dermatophyte hyphae. Tunnels, regularly placed next to each other, create white transverse streaks visible to the naked eye, which when viewed through a magnifying glass give an image the so-called Alkiewicz’s transverse mesh.

Much less often, as a result of the penetration of a dermatophyte from the side of the infected cuticle (eponychium) into the soft nail plate in this area, the result is described by Sowiński the so-called twig meshpenetrating through its branches to the nail root. Symptoms of the meshes are pathognomonic for nail dermatophytosis, which allows its diagnosis in this part of cases where mycological cultures remain negative. This characteristic picture of the nail grids depends mainly on the enzymatic activity of the dermatophytes.

In those cases where it occurred infection with a dermatophyte with low enzymatic activity, the fungus attacks the more accessible keratin in the intercellular spaces for a long time and almost exclusively, creating the channels already described. The clinical picture and the course of the infection are completely different, when the infecting dermatophyte shows significant enzymatic activity. It also attacks the keratin inside the nail cells, and very quickly the nail structure disintegrates significantly and the plate frequently crumbles from the side of its free edge.

In cases of onychomycosis caused by fungi with high enzymatic activity, mesh symptoms are usually sporadic and in the initial stage of the disease, as their regular structure is quickly destroyed due to the progressive invasion of the fungus. Due to the high enzymatic activity of the dermatophyte, its hyphae also grow in the epidermis of the placenta, which causes its protective reaction. The result is pathological keratosis of the placenta, clinically expressed by a loss of transparency and a change in pink color under the nail plate. Under these conditions, the layers of horny cells under the nail are interspersed with threads of the fungus and therefore loosely woven. This results in weaker bonding of the nail with the base, which may further cause onycholysis, i.e. the separation of the nail plate from the bed.

Dermatophyte mycosis of the nails – symptoms of ailments

Dermatophyte mycosis of the nails affects the toenails more often than the toenails. It is related to slower growth of toenails and it is much more common on the feet than on the hands, which is one of the leading causes of nail infections. Blood circulation disorders in the foot area, often aggravated by the pressure of tight shoes, favoring the development of mycosis are also not uncommon. This explains, among other things, the fact that onychomycosis usually begins in the toe and fifth finger nails.

Dermatophytes develop mainly in the deeper layers of the nail plate, because they have the best conditions for development there. A role in this is played by the reduced cohesion of the soft bearing layer of the plaque made of young keratin and a greater degree of its moisture near the placenta.

The clinical pictures of onychomycosis largely depend on the place where the fungus enters the nail organ. Based on this, most mycologists now distinguish hers four main characters:

1. Distal and lateral sub-plaque onychomycosis (distal and lateral subungual onychomycosis – DLSO). It is by far the most common form of dermatophytosis of the nails. In this clinical form, the dermatophyte penetrates the bed and the nail plate under the free edge of the nail or from the side of the lateral shafts. There is a significant keratosis of the sub-platelet placenta, which in turn leads to loss of nail clarity and frequent onycholysis. In rare cases, in the course of chronic inflammation of the placenta, a blood vessel may rupture, showing up under the nail as dashed hematomas. The nail plate occupied by the dermatophyte becomes matte with a whitish-yellow shade, easily crumbles, its free edge is frayed and “recedes” due to breaking and gradual separation of the plate, revealing the bed with horn masses. The white, speckled discoloration of the plates (leukonychia mycotica), which is found only in some cases, is a consequence of the significant compaction of the previously described tunnels, which make up the image of the meshes visible under the magnifying glass. As the disease progresses, the plaque usually crumbles and becomes dirty gray at the edges of the cavities.
2. Proximal sub-platelet onychomycosis (proximal subungual onychomycosis — PSO). It is a rarer form of nail dermatophytosis. In this form of the disease, the dermatophyte most often penetrates into the softer plate on the proximal nail fold side. This happens especially when, for cosmetic reasons, the helix (eponychium) that seals the space between the plate and the nail shaft is removed. This type of mycosis is also more common in HIV-infected patients. The disease usually begins as a white spot in the proximal part of the plaque (leukonychia mycotica), which when viewed under a magnifying glass gives an image of the twig mesh tunnels. Later, the fungus penetrates into the deep layers of the plate and the placenta, occupying the entire nail which grows back, causing the keratosis of the placenta, typical of dermatophyte mycosis, and finally separation and chipping of the nail plate. The form of proximal subungual onychomycosis spreading through the lymphatic pathway, described mainly by mycologists, is very rare. What is striking in the clinical picture is the symmetry of the nail lesions on the feet with the almost simultaneous involvement of a significant number of plates.
3. Intra-plaque onychomycosis (endonyx onychomycosis — EO). The white, speckled discoloration of the plaques (leukonychia mycotica) encountered in these cases is a consequence of the significant compaction of the tunnels hollowed out by the fungus, which make up the mesh symptom visible under the magnifying glass, characteristic only for dermatophyte mycosis of the nails. In most of these cases, there was an infection with a dermatophyte with low enzymatic activity and for a very long time the fungus attacks almost exclusively the more easily available keratin in the intercellular spaces, creating characteristic channels inside the nail plate, most often without inflammation of the placenta, and therefore without subungual keratosis.
4. White superficial onychomycosis (white superficial onychomycosis – WSO). This form of dermatophyte mycosis occurs only on the toenails. The isolation of white superficial onychomycosis as a separate form of onychomycosis is not fully accepted by all mycologists, because such lesions can also cause nondermatophytes, and besides, it can be found in one nail plate next to the typical foci of distal and proximal subungual onychomycosis. Zaias considers white superficial onychomycosis to be very common, but usually unnoticed because it causes minor symptoms and slightly damages the nail plate. In the clinical picture, these are white powdery spots on the surface of the nail that blend together, which when viewed with a magnifying glass do not give a specific image of the mesh. Penetration of dermatophytes deep into the plaque is minimal here, as fungi in the dorsal part of the plaque face unfavorable development conditions and therefore the pathogenesis of the above changes is dominated by a saprophytic model of fungal growth.

In advanced cases of dermatophyte mycosis of the nails, it is rarely possible to distinguish the type of invasion, because the nail plates can be significantly damaged, up to their complete separation and chipping, including an image when only covered ones, including such an image, can be seen, when only covered masses can be seen. horny nail bed: completely dystrophic onychomycosis (total dystrophic onychomycosis — TDO).

Dermatophytes can also invade previously changed nail plates in the course of many diseases in which destructive changes occur in the nail organ. These diseases include mainly:

1. psoriasis
2. lichen planus,
3. Darier’s disease.

They can also penetrate dystrophically changed, often onycholytic nails in the course of impaired peripheral circulation of the limbs, as well as destructively changed plaques in eczema, alopecia areata or diabetes.

1. Buy an intensive conditioner for nails with psoriasis EPTA PSO today at medonetmarket.pl – separately or in a set with 30% urea for body and nail care with psoriasis EPTA PSO 30.

Diagnostics of nail dermatophytosis

In rare cases, to confirm the fungal infection in the nails, histopathological examinations are performed with the use of staining with the PAS method (periodic acid schiff). After applying this staining, the cell walls of fungi containing mucopolysaccharides stain dark red with fuchsin, which contrasts with the much weaker staining of the surrounding structures of the nail.

In some patients, the diagnosis can be made after finding during watching under a magnifying glass the symptom of a transverse or twig net already described. These symptoms are pathognomonic and allow the diagnosis of dermatophytosis of the nails, if we detect them in a patient at least in one of the affected nail plates.

However, the main criterion for the diagnosis of nail dermatophytosis and the implementation of appropriate treatment is isolation and identification of the fungus. Proper collection of the material for testing is of key importance for obtaining the correct result, because in dermatophyte mycosis of the nails, the infection develops mainly in the inaccessible placental part of the nail plate. That is why an incorrect test technique, and in particular a too superficial sample collection, may result in false-negative results.

In order to reach the deeper layers of nail keratin near the bed, you can pick up material with an electric drill. An additional advantage of this method is the high degree of fragmentation of the material taken from the nail plates, which also increases the chance of isolating the pathogen. The collected material is routinely viewed under a microscope in the form of direct preparations. Such a preparation is prepared using a 20% KOH solution with the addition of 40% DMSO (dimethylsulfoxide), which is a reagent that loosens the keratinized structures of the collected nail material. This test allows for an approximate assessment of whether there are threads of fungi in a given material.

In any case, it is carried out inoculation of the collected material.

Cultivation for dermatophytes (with actidione and chloramphenicol) takes three to four weeks. After the fungal growth has been obtained, the subsequent determination of the dermatophyte strains is for formation slide micro-cultures i exploitation auxiliary media.

The appearance of macroconidia and microconidia as well as residual fruiting bodies that are products of vegetative mycelium are the basis for the diagnosis of dermatophytes. The supporting media is mainly used with the DTM (dermatophyte test medium). This medium makes it possible to distinguish dermatophytes from other fungi as it turns from yellow to red in the presence of dermatophytes.

It is also used Christensen’s broth with ureathe color of which turns Trichophyton mentagrophytes red due to the production of urease, which distinguishes it from Trichophyton rubrum, which does not produce urease. In cases of extensive and recurrent dermatophyte mycosis of the nails, it seems advisable to determine the in vitro antifungal activity of the drugs that we want to use in the planned treatment. These tests can be performed by the slide micro culture method or by the disc diffusion method.

Differentiation with other ailments

In addition to nail lesions caused by other pathogenic fungi, the differentiation of non-fungal nail diseases should primarily include:

1. nail psoriasis,
2. nail lichen planus,
3. rough nails,
4. nail vitiligo,
5. dystrophic changes in the nails in the course of eczema and alopecia areata.

The decisive factor for the diagnosis is the statement symptom of a transverse or twig net when viewing the nails under a magnifying glass and obtaining a fungus culture from the material taken from the nails.

Dermatophytosis of the nails – treatment

In local treatment The following preparations are recommended for dermatophyte mycosis of the nails:

1. amorolfina,
2. ciclopirox.

These preparations are recommended for use on infected nails in the form of a varnish applied twice a week for a period of 6 months – in onychomycosis of the hands up to 12 months – in onychomycosis of the feet.

In general uprising dermatophyte mycosis of the nails, three preparations are currently used for oral administration:

1. itraconazole,
2. fluconazole,
3. terbinafine,

Check it out: Which drugs contain itraconazole?

In the case of fluconazole a much longer treatment is usually recommended (at least 3 months in the case of onychomycosis of the hands and from 6 to even 12 months in the case of onychomycosis). This drug is normally administered at a dose of 150 mg / week, with the higher dose (300-450 mg / week) increasing its platelet concentration and treatment efficacy.

The drug with the broadest spectrum of activity among the third generation triazole derivatives recommended for the treatment of onychomycosis is itraconazole. It is administered orally at a dose of 200 mg daily for 6 weeks in onychomycosis and for 12 weeks in onychomycosis. Most often, however, this drug is administered using the pulse method (2 x 200 mg / day for 1 week a month) – 2 pulses are recommended for onychomycosis of the hands, and 3 pulses for onychomycosis.

The second, next to itraconazole, drug that is currently of fundamental importance in the treatment of onychomycoses is terbinafine belonging to allylamines. It is administered at a dose of 250 mg / day for 6 weeks in onychomycosis and 12 weeks in onychomycosis.

Pulse treatment regimens at a dose of 250 mg daily for 7 days a month, repeated for 2 or 3 months for a period of 24 to 26 months, are also proposed.

There is also a modification general antifungal monotherapy referred to as adjunctive therapy, where, in addition to the standard pulse treatment with itraconazole, Sabouraud agar is applied to the affected nail plates for 48 hours a week after the end of each pulse. This type of procedure is explained by the assumption that the cause of treatment failures is the presence of spore forms of the fungus in the nails, which are insensitive to the drug used, and the application of Sabouraud agar on the plates is to stimulate the fungi to transform into susceptible forms and significantly improve the effectiveness of the therapy.

In children over 2 years of age, terbinafine is mainly used in dermatophyte mycosis of the nails at a dose of 62,5 mg / day (with a body weight of up to 20 kg) and 125 mg / day (with a body weight of 20-40 kg), and the treatment period is the same as in adults.

The new, quite effective and broad-spectrum antifungal activity also works well in onychomycosis preparat triazolowy second generation called rawuconazole. It is administered at a dose of 200 mg / day for twelve weeks and has a lower affinity for the CYP3A4 enzyme than other triazoles, which should limit its interactions with other drugs.

Read more: Medicines for onychomycosis – how to choose the best?

Currently, it is widely believed that the most effective therapy in nail dermatophytosis is combination therapy based on a combination of general and local treatment. This applies especially to extensive and recurrent dermatophyte mycosis of the toenails and mixed nail infections in which, apart from dermatophytes, there are yeast-like mushrooms or mold. In these patients, a combination therapy can be successfully used, in which oral administration of terbinafine or itraconazole for 3 months is combined with external application of amorolfine or ciclopirox varnish applied 1-2 times a week for 6-12 months to the nail plates. It is also proposed sequential therapywhich may be referred to as a variant of combination therapy. In this case, two oral preparations are used, e.g. 2 pulses of itraconazole and 1 pulse of terbinafine, which is to give better treatment results than monotherapy.

It is also believed that – especially in the elderly – it is beneficial to combine oral antifungal drugs with the improvement of peripheral blood circulation in the limbs pentoxifylline, recommended in a dose of 2 mg twice a day for 400 months.

There may also be an alternative and fully effective method to the treatment methods already described, especially for recurrent onychomycosis surgical removal of nail plates combined with daily oral administration of terbinafine or itraconazole and careful external treatment after surgery. In these cases, terbinafine is administered at a dose of 250 mg daily and itraconazole 200 mg daily for 4 weeks after surgery.

External treatment consists in applying 5% to the nail bed in the first week after the procedure. sterile salicylic ointment with simultaneous cover of nail shafts with zinc paste. In the following weeks, it is recommended to wipe the bearings with 3% resorcinol spirit and 3% iodine tincture, and lubricate them with Whitfield ointment. In order to obtain the correct regrowth of the nail plates, it is also important to frequently clean the exposed nail beds of accumulated horny masses. These treatments are usually performed every 2 weeks after bathing the limbs.

An important supplementary element in the treatment of nail dermatophytosis is properly carried out disinfection of shoes, socks and glovesbecause dermatophytes can survive in contaminated shoes or gloves for many months and incorrect disinfection is a common cause of treatment failure.

What’s the prognosis?

In most cases, treatment of nail dermatophytosis leads to its complete resolution. Rating the effectiveness of the treatment of onychomycosis however, it is very different, which depends not only on the method of treatment and the drug used, but also on the clinical form of the infection, its extent and the age and general condition of the patients treated, as well as on the enzymatic properties of the infecting fungi.

Also read:

1. Nail diseases – how to recognize them?
2. Nail fungus – types, causes, treatment, prevention
3. Candidiasis of nail plates and shafts

The content of the medTvoiLokony website is intended to improve, not replace, the contact between the Website User and their doctor. The website is intended for informational and educational purposes only. Before following the specialist knowledge, in particular medical advice, contained on our Website, you must consult a doctor. The Administrator does not bear any consequences resulting from the use of information contained on the Website.