The term onychomycosis (fungus of the fingernails and toenails) describes a fungal infection of the nail caused by dermatophytes, non-dermatophyte molds, or yeasts. There are four clinically distinct forms of onychomycosis. Diagnosis is based on CON examination, microscopic and histological examination. Most often, treatment involves systemic and local therapy, sometimes using surgical removal.
Factors contributing to the development of nail fungus
- Increased sweating (hyperhidrosis).
- Vascular insufficiency. Violation of the structure and tone of the veins, especially in the veins of the lower limbs (characteristic of onychomycosis of the toenails).
- Circle. The incidence of the disease in humans increases with age. In 15-20% of the population, the pathology appears at the age of 40-60.
- Diseases of internal organs. Disorders of the nervous system, endocrine (onychomycosis occurs most often in diabetics) or immune system (immunosuppression, especially HIV infection).
- A large nail mass consisting of a thick nail plate and the contents underneath can cause discomfort when wearing shoes.
- Traumatization. Permanent trauma or damage to the nail and lack of proper treatment.
The prevalence of the disease
Onychomycosis– the most common nail disease, which is the cause of 50% of all onychodystrophies (destruction of the nail plate). It affects up to 14% of the population, and both the prevalence of the disease in older people and its overall incidence are increasing. The incidence of onychomycosis is also increasing among children and adolescents, with onychomycosis accounting for 20% of dermatophyte infections in children.
The increase in the prevalence of the disease is associated with the wearing of tight shoes, the increase in the number of people receiving immunosuppressive treatment, and the increased use of public changing rooms.
Nail disease usually begins with tinea pedis before spreading to the nail bed, where eradication is difficult. This area serves as a reservoir for local relapses or spread of infection to other areas. Up to 40% of patients with onychomycosis of the toes have a combined skin infection, most commonly tinea pedis (about 30%).
The causative agent of onychomycosis
In most cases, onychomycosis is caused by dermatophytes, T. rubrum and T. interdigitale are the causative agents of the infection in 90% of cases. T. tonsurans and E. floccosum have also been documented as etiological agents.
Yeasts and non-dermatophyte molds such as Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis and Scytalidium are the source of onychomycosis of the toes in about 10% of cases. It is interesting to note that in 30% of onychomycosis of the fingers, Candida species are the causative agents, while non-dermatophyte molds are not found in the affected nails.
Pathogenesis
Dermatophytes have a number of enzymes that function as virulence factors and ensure the attachment of the pathogen to the nails. The first stage of infection is adhesion to keratin. Due to the further breakdown of keratin and the gradual release of mediators, an inflammatory reaction develops.
The stages of the pathogenesis of a fungal infection are as follows.
Adhesion
Fungi overcome several lines of host defense before hyphae survive in keratinized tissues. The first is the successful adhesion of arthroconidia to the surface of keratinized tissues. Early nonspecific lines of host defense include fatty acids in tallow and competitive bacterial colonization.
Recently, several studies have investigated the molecular mechanisms of arthroconidia adhesion to keratinized surfaces. Dermatophytes have been shown to selectively use their proteolytic reserves during adhesion and invasion. Some time after adhesion occurs, the spores germinate and proceed to the next stage - invasion.
Invasion
Traumatization and maceration are favorable environments for fungal invasion. Invasion of the germinating elements of the fungus results in the release of various proteases and lipases, usually various products that serve as nutrients for the fungi.
The owner's reaction
Fungi face several defense barriers in the host, such as inflammatory mediators, fatty acids, and cellular immunity. The first and most important barrier is the keratinocytes, which are encountered by the invading fungal elements. The role of keratinocytes: proliferation (increasing exfoliation of cortical scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As the fungus penetrates deeper, more and more new, non-specific mechanisms are activated for protection.
The severity of the host's inflammatory response depends on the immune status and the natural habitat of the dermatophytes involved in the invasion. The next level of defense is the delayed-type hypersensitivity reaction, which is caused by cell-mediated immunity.
The inflammatory response associated with this hypersensitivity is associated with clinical destruction, while a defect in cell-mediated immunity can lead to chronic and recurrent fungal infection.
Despite epidemiological observations suggesting a genetic predisposition to fungal infection, there are no molecularly proven studies.
Clinical picture and symptoms of foot and nail damage
The infection has four characteristic clinical forms. These forms can be isolated or include several clinical forms.
Distal-lateral subungual onychomycosis
This is the most common form of onychomycosis and can be caused by any of the pathogens listed above. It begins with the invasion of the pathogen in the stratum corneum of the hyponychium and the distal nail bed, resulting in a whitish or brownish-yellow discoloration of the distal end of the nail. The infection then spreads proximally up the nail bed to the ventral side of the nail plate.
Hyperproliferation or dedifferentiation of the nail bed as a result of the response to infection causes subungual hyperkeratosis, while progressive invasion of the nail plate leads to increased nail dystrophy.
Proximal subungual onychomycosis
It develops as a result of infection of the proximal nail fold, primarily by T. rubrum and T. megninii organisms. Clinic: darkening of the proximal part of the nail with a white or beige shade. This clouding gradually increases to cover the entire nail, eventually leading to leukonychia, proximal onycholysis, and/or destruction of the entire nail.
Patients with proximal subungual onychomycosis should be tested for HIV infection, as this form is a marker of the disease.
White superficial onychomycosis
It develops as a result of direct invasion of the dorsal nail plate and appears as white or pale yellow, well-defined spots on the surface of the nail. The causative agents are usually T. interdigitale and T. mentargophytes, although non-dermatophyte molds such as Aspergillus, Fusarium and Scopulariopsis are also known to cause this form. Candida species can penetrate the hyponychium of the epithelium and eventually infect the nail through the entire thickness of the nail plate.
Candida onychomycosis
Damage to the nail plate caused by Candida albicans is only observed in cases of chronic mucocutaneous candidiasis (a rare disease). All nails are usually affected. The nail plate thickens and acquires various shades of yellow-brown color.
Diagnosis of onychomycosis
Although onychomycosis accounts for 50% of nail dystrophic cases, it is advisable to obtain laboratory confirmation of the diagnosis before starting toxic systemic antifungal drugs.
Examination of the masses under the nail with KOH, culture analysis of the material of the nail plate and masses under the nail on Sabouraud dextrose agar (with and without antimicrobial additives), and staining of nail clippings with the PAS method are the most informative methods.
Study the CON
This is a standard test for suspected onychomycosis. However, it often gives a negative result even in cases of high clinical suspicion, and cultural analysis of nail material in which hyphae were found during examination with CON is often negative.
The most reliable way to minimize false negative results due to sampling errors is to increase the sample size and repeat the sampling.
Cultural analysis
This laboratory test determines the type of fungus and determines the presence of dermatophytes (organisms that respond to antifungal drugs).
We recommend the following recommendations for distinguishing between pathogens and pollutants:
- if the dermatophyte is isolated in culture, it is considered pathogenic;
- Non-dermatophytic molds or yeasts isolated in culture are only relevant if hyphae, spores or yeast cells are observed under the microscope and repeated active growth of the non-dermatophytic mold pathogen is observed without isolation.
Cultural analysis, PAS - the staining method of nail clipping is the most sensitive and does not require waiting for several weeks for the result.
Histological examination
During the histopathological examination, the hyphae are located between the layers of the nail plate, parallel to the surface. Spongiosis and focal parakeratosis, as well as an inflammatory reaction, can be observed in the epidermis.
In the case of superficial white onychomycosis, the microorganisms are found superficially, at the back of the nail, showing the pattern of their unique "perforating organs" and modified hyphal elements, so-called "bitten leaves". In case of Candida onychomycosis, invasion of pseudohyphae is observed. Histological examination of onychomycosis is performed with special dyes.
Differential diagnosis of onychomycosis
| The most likely | Sometimes it is likely | Rarely found |
|---|---|---|
|
|
Melanoma |
Treatment methods for nail fungus
Treatment of toenail fungus depends on the severity of the nail injury, the presence of associated tinea pedis, and the effectiveness and possible side effects of the treatment regimen. If the involvement of the nail is minimal, localized therapy is a rational decision. In combination with dermatophytosis of the feet, especially against the background of diabetes, it is absolutely necessary to prescribe therapy.
Topical antifungal agents
For patients with distal involvement of the nail or for whom systemic therapy is contraindicated, topical therapy is recommended. However, we must remember that only local therapy with antifungal agents is not effective enough.
Lacquer belonging to the oxypyridone group is becoming more and more popular, and is used daily for 49 weeks. In the case of mild or moderate onychomycosis caused by dermatophytes, about 40% of patients achieve mycological cure, and 5% achieve nail cleaning (clinical cure). .
Despite its much lower efficacy compared to systemic antifungal drugs, the topical application of the drug avoids the risk of drug-drug interactions.
Another specially developed drug in the form of nail polish is used twice a week. A representative of a new class of antifungal drugs, morpholine derivatives, active against yeasts, dermatophytes and molds that cause onychomycosis.
The mycological binding rate of this product may be higher than the previous varnish; however, controlled studies are needed to determine a statistically significant difference.
Antifungals for oral administration
Systemic antifungal medication is required for onychomycosis involving the matrix area, or if shorter treatment or a greater chance of clearance and healing is required. When choosing an antifungal drug, the etiology of the pathogen, possible side effects, and the risk of drug interactions for each patient must be taken into account.
A fungistatic and fungicidal drug belonging to the allylamine group against dermatophytes, Aspergillus is less effective against Scopulariopsis. The product is not recommended for candidal onychomycosis, because it shows variable effectiveness against Candida species.
For most toenail injections, the standard 6-week dose is effective, while toenail injections require at least 12 weeks. Most side effects are related to digestive problems, including diarrhea, nausea, taste changes, and increased liver enzymes.
Data show that a 3-month continuous regimen is currently the most effective systemic therapy for toenail onychomycosis. The clinical cure rate in various studies is approximately 50%, although the treatment rate is higher in patients over 65 years of age.
A drug belonging to the azole group, which has a fungistatic effect against dermatophytes and non-dermatophyte molds and yeasts. Safe and effective regimens include daily pulse dosing for one week per month or continuous daily dosing, both of which require a two-month cycle of therapy for nails and at least three months or three pulses of treatment.
For children, the medicine is dosed individually depending on the weight. Although the drug has a wider spectrum of action than its predecessor, studies have shown significantly lower cure rates and higher relapse rates.
Elevated liver enzymes occur in less than 0. 5% of patients during treatment and normalize within 12 weeks after stopping treatment.
Fungistatic drug against dermatophytes, some non-dermatophyte molds and Candida species. This medicine is usually taken once a week for 3 to 12 months.
There are no clear criteria for laboratory monitoring of patients receiving the above drugs. Before treatment and 6 weeks after starting treatment, it is advisable to perform a complete blood count and liver function tests.
The drug belonging to the grisan group is no longer considered a standard therapy for the treatment of onychomycosis due to long treatment, possible side effects, drug-drug interactions and a relatively low cure rate.
Combination therapy may result in higher clearance rates than systemic or topical treatment alone. Taking an allylamine drug in combination with morpholine varnish results in clinical cure and a negative mycological test in approximately 60% of patients, compared with 45% of patients receiving a systemic allylamine antifungal agent alone. However, another study found no additional benefit when a systemic allylamine drug was combined with a solution of the drug oxypyridone.
Other medicines
The antifungal effect demonstrated in vitro for thymol, camphor, menthol and Eucalyptus citriodora oil indicates the possibility of additional therapeutic strategies in the treatment of onychomycosis. An alcoholic solution of thymol can be applied in the form of drops to the nail plate and hyponychia. The application of topical thymol preparations to the nails results in healing in individual cases.
Surgery
Final treatment options for treatment-resistant cases include surgical removal of the nail with urea. To remove the crumbly mass from the affected nail, special forceps are used.
Many doctors believe that the main and first way to treat nail fungus is the mechanical removal of the nail. Most often, surgical removal of the affected nail is recommended, less often with the help of keratolytic patches.
Traditional methods in the fight against nail fungus
Despite the large number of different folk recipes for the removal of nail fungus, dermatologists do not recommend choosing this treatment option and starting "home diagnosis". It is wiser to start therapy with local drugs that have undergone clinical trials and proven to be effective.
Course and prognosis
Poor prognostic signs are nail plate thickening, secondary bacterial infection, and pain due to diabetes mellitus. The most beneficial way to reduce the likelihood of relapse is to combine treatment methods. Onychomycosis therapy is a long journey that does not always lead to complete recovery. However, do not forget that the effect of systemic therapy is up to 80%.
Prevention
Prevention includesmany events, thanks to which you can significantly reduce the percentage of onychomycosis infection and reduce the likelihood of relapse.
- Disinfection of personal and public objects.
- Systematic disinfection of shoes.
- Treatment of legs, hands, folds (under favorable conditions - favorite localization) with local antifungal agents on the recommendation of a dermatologist.
- If the diagnosis of onychomycosis is confirmed, it is necessary to consult a doctor for a check-up every 6 weeks and at the end of systemic therapy.
- If possible, disinfect the nail plates at each medical visit.
Conclusion
Onychomycosis (fingernail and toenail fungus) is an infection caused by various fungi. This disease affects the nail plate of the fingers or toes. When making a diagnosis, examine all skin and nails and rule out other diseases that mimic onychomycosis. If there is doubt about the diagnosis, it should be confirmed either by culture (preferably) or by histological examination of nail clippings followed by staining.
Therapy includes surgical removal, local and general medications. The treatment of onychomycosis is a long process that can take several years, so you should not expect a cure from "one pill". If you suspect nail fungus, consult a specialist to confirm the diagnosis and prescribe an individual treatment plan.