The term onychomycosis (toenail and toenail fungus) describes a fungal nail infection caused by dermatophytes, non-dermatophytic molds, or yeasts. There are four clinically distinct forms of onychomycosis. Diagnosis of CON is based on microscopic and histological examination. Often, treatment includes systemic and local therapy, sometimes surgical removal is resorted to.
Factors that cause nail fungus
- Increased sweating (hyperhidrosis).
- Vascular insufficiency. Violation of the structure and tone of the veins, especially the veins of the lower extremities (typical of toenail onychomycosis).
- Age. In humans, the frequency of the disease increases with age. In 15-20% of the population, the pathology occurs at the age of 40-60.
- Diseases of internal organs. Disorders of the nervous, endocrine (onychomycosis occurs most often in people with diabetes) or immune (immunosuppression, especially HIV infection) systems.
- A large nail mass, consisting of a thick nail plate and the contents below it, can cause discomfort when wearing shoes.
- Traumatization. Permanent trauma to the nail or injury and lack of proper treatment.
Disease spread
Onychomycosis– the most common nail disease, the cause of 50% of all cases of onychodystrophy (destruction of the nail plate). It affects up to 14% of the population, and both prevalence and overall incidence are increasing in the elderly. The frequency of onychomycosis in children and adolescents is also increasing, with onychomycosis accounting for 20% of dermatophyte infections in children.
The increased prevalence may be related to wearing narrow shoes, the number of people receiving immunosuppressive therapy, and the increased use of public locker rooms.
Nail disease usually begins with tinea pedis before spreading to the nail bed, where it is difficult to eradicate. This area acts as a reservoir for local recurrences or spread of infection to other areas. 40% of patients with onychomycosis on the toes have associated skin infections, most commonly tinea pedis (about 30%).
The causative agent of onychomycosis
In most cases, onychomycosis is caused by dermatophytes, with T. rubrum and T. interdigitale causing the infection in 90% of all cases. T. tonsurans and E. floccosum have also been documented as etiologic agents.
Yeast and non-dermatophyte mold organisms such as Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis, and Scytalidium are the source of toe onychomycosis in about 10% of cases. Interestingly, Candida species are causative in 30% of cases of onychomycosis of the fingers, whereas non-dermatophytic molds are not found in affected nails.
Pathogenesis
Dermatophytes, acting as virulence factors, have a wide range of enzymes that allow the pathogen to adhere to the nails. The first stage of infection is adhesion to keratin. An inflammatory reaction develops due to the further breakdown of keratin and the cascade release of mediators.
The stages of the pathogenesis of fungal infection are as follows.
Don't stick
Fungi overcome several host defense lines before hyphae can 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 sebum as well as competitive bacterial colonization.
Several recent studies have investigated the molecular mechanisms involved in the adhesion of arthroconidia 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 move to the next stage - invasion.
Invasion
Traumatization and maceration are favorable environments for fungal penetration. Invasion of the germinating elements of fungi ends with the release of various proteases and lipases, and various products that generally serve as food for fungi.
The owner's reaction
Fungi face many protective barriers within the host, such as inflammatory mediators, fatty acids, and cellular immunity. The first and most important barrier is the keratinocytes that encounter the invasion of fungal elements. The role of keratinocytes: proliferation (to promote desquamation of horny 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, as well as the natural habitat of the invading dermatophytes. The next level of defense is the delayed-type hypersensitivity reaction, which is caused by cell-mediated immunity.
The inflammatory response associated with this sensitivity is associated with clinical destruction, a defect in cellular 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 presentation and symptoms of toenail and nail lesions
There are four characteristic clinical forms of infection. These forms can be isolated or contain several clinical forms.
Distal-lateral subungual onychomycosis
It is the most common form of onychomycosis and can be caused by any of the pathogens listed above. Hyponychia begins with pathogen invasion of the stratum corneum of the distal nail bed, resulting in whitish or brownish-yellow discoloration of the distal end of the nail. The infection then spreads proximally from the nail bed to the ventral side of the upper nail plate.
Hyperproliferation or impaired differentiation of the nail bed in response to infection leads to subungual hyperkeratosis, and progressive invasion of the nail plate leads to increased nail dystrophy.
Proximal subungual onychomycosis
It is mainly caused by infection of the proximal nail bed by the organisms T. rubrum and T. megninii. Clinic: clouding of the proximal part of the nail with white or beige color. This opacification gradually increases and involves the entire nail, eventually leading to leukonychia, proximal onycholysis, and/or destruction of the entire nail.
Patients with proximal subungual onychomycosis should be screened for HIV infection, as this form is considered a marker for this disease.
White superficial onychomycosis
It results from direct invasion of the dorsal nail plate and appears as white or dull yellow, well-defined spots on the surface of the toenail. The pathogens are usually T. interdigitale and T. mentargophytes, although non-dermatophyte molds such as Aspergillus, Fusarium and Scopulariopsis are also pathogens of this form. Candida species can invade the hyponych of the epithelium and eventually infect the nail through the entire thickness of the nail plate.
Candidal onychomycosis
Damage to the nail plate caused by Candida albicans is observed only in chronic mucocutaneous candidiasis (a rare disease). Usually all nails are affected. The nail plate thickens and acquires different shades of yellow-brown color.
Diagnosis of onychomycosis
Although onychomycosis accounts for 50% of cases of nail dystrophy, it is advisable to get laboratory confirmation of the diagnosis before starting toxic systemic antifungal drugs.
Examination of subungual masses with KOH, cultural analysis of the material of the nail plate on Sabouraud dextrose agar (with and without antimicrobial additives), and staining of nail scraps by the PAS method are the most informative methods.
Study with CON
It is a standard test for suspected onychomycosis. However, it often gives a negative result even with a high clinical suspicion, and cultural analysis of the nail material in which hyphae are detected during the study with CON is often negative.
The surest way to minimize false negatives due to sampling errors is to increase the sample size and replicate the sample.
Cultural analysis
This lab test identifies the type of fungus and detects the presence of dermatophytes (organisms that respond to antifungal drugs).
The following recommendations are suggested for distinguishing pathogens from contaminants:
- a dermatophyte is considered pathogenic if isolated in culture;
- Nondermatophytic mold or yeast organisms isolated in culture are relevant only when hyphae, spores, or yeast cells are observed under the microscope and repeated active growth of the nondermatophytic mold pathogen is observed without isolation.
Cultural analysis, PAS - nail scraping staining method is the most sensitive and does not require waiting for results for several weeks.
Pathohistological examination
During pathohistological examination, hyphae are located between the layers of the nail plate, parallel to the surface. In the epidermis, spongiosis and focal parakeratosis, as well as an inflammatory reaction, can be observed.
In superficial white onychomycosis, the organisms are found superficially on the back of the nail, displaying their unique pattern of "perforating organs" and modified hyphal elements called "bitten leaves. "Invasion of pseudohyphae is observed with candidal onychomycosis. Histological examination of onychomycosis occurs with special dyes.
Differential diagnosis of onychomycosis
| Likely | Sometimes likely | Rarely found |
|---|---|---|
|
|
Melanoma |
Methods of treatment of nail fungus
Treatment of nail fungus depends on the severity of the nail lesion, the presence of associated tinea pedis, and the effectiveness and potential side effects of the treatment regimen. If nail involvement is minimal, localized therapy is a rational decision. When combined with dermatophytosis of the feet, it is mandatory to prescribe therapy, especially against the background of diabetes mellitus.
Local antifungal drugs
Local therapy is recommended in patients with distal nail involvement or contraindications for systemic therapy. But we must remember that only local therapy with antifungal agents is not effective enough.
Varnish from the oxypyridone group is becoming increasingly popular, applied daily for 49 weeks, mycological cure is achieved in about 40% of patients, nail cleaning (clinical cure) in 5% of cases of mild or moderate onychomycosis caused by dermatophytes. .
Despite the lower effectiveness compared to systemic antifungal drugs, the local use of the drug avoids the risk of drug-drug interactions.
Another specially prepared drug in the form of nail polish is used 2 times a week. Morpholine derivatives are a representative of a new class of antifungal drugs active against yeasts, dermatophytes, and molds that cause onychomycosis.
This product may have higher mycological treatment rates than the previous varnish; however, controlled studies are needed to determine a statistically significant difference.
Antifungal drugs for oral administration
In cases of onychomycosis involving the matrix area or when a shorter course of treatment or a higher chance of clearance and recovery is desired, a systemic antifungal drug is necessary. When choosing an antifungal drug, first of all, it is necessary to consider the etiology of the pathogen, potential side effects and the risk of drug interaction in each individual patient.
A drug from the allylamine group, which has a fungistatic and fungicidal effect against dermatophytes, Aspergillus, is less effective against Scopulariopsis. The product is not recommended for candidal onychomycosis because it has variable activity against Candida species.
A standard dose of 6 weeks is effective for most toenail injections, while a minimum of 12 weeks is required for toenails. Most side effects are related to digestive problems, including diarrhea, nausea, taste changes, and increased liver enzymes.
Data indicate that a 3-month continuous dosing regimen is currently the most effective systemic therapy for onychomycosis of the toenails. In various studies, the clinical cure rate is about 50%, although cure rates are higher in patients older than 65 years.
A drug from the azole group that has a fungistatic effect against dermatophytes, as well as non-dermatophyte mold and yeast organisms. Safe and effective regimens include once-a-month daily pulse dosing or continuous daily dosing, both of which require two months or two cycles of therapy for fingernails and at least three months or three pulses of therapy for toenail lesions.
In children, the drug is prescribed individually depending on the weight. Although the drug has a wider spectrum of action than its predecessor, studies have shown significantly lower rates of treatment with it and a higher relapse rate.
Liver enzyme elevations occur in less than 0. 5% of patients during therapy and return to normal within 12 weeks after discontinuation of therapy.
A drug with a fungistatic effect against dermatophytes, some non-dermatophytic fungi 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 taking the above drugs. Complete blood count and liver function tests are reasonable before treatment and 6 weeks after starting treatment.
A drug from the Grisan group is no longer considered a standard therapy for onychomycosis due to the long course of treatment, potential side effects, drug-drug interactions, and relatively low cure rates.
Combination treatment regimens may produce higher clearance rates than single systemic or topical therapy. Administration of allylamine in combination with morpholine varnish resulted in clinical recovery and a negative mycological test in approximately 60% of patients, compared with 45% of patients receiving systemic allylamine antifungal agents alone. However, another study showed no additional benefit when combining a systemic allylamine agent with oxypyridone solution.
Other medicines
The in vitro fungicidal activity shown for thymol, camphor, menthol, and eucalyptus citriodora oil suggests the potential for additional therapeutic strategies in the treatment of onychomycosis. An alcohol solution of thymol can be used in the form of drops on the nail plate and hyponychia. The use of local preparations with thymol for nails leads to treatment in isolated cases.
Surgery
Final treatment options for refractory cases include surgical removal of the nail with urea. Special nippers are used to remove the mass that breaks down from the affected nail.
Many doctors believe that the main and first method of treating nail fungus is the mechanical removal of the nail. Surgical removal of the affected nail is often recommended, and less often, removal using keratolytic patches.
Traditional methods in the fight against nail fungus
Despite the large number of different folk recipes to eliminate nail fungus, dermatologists do not recommend choosing this treatment option and starting with "home diagnosis". It is wiser to start therapy with local drugs that have been clinically tested and proven to be effective.
Course and forecast
Poor prognostic signs include thickening of the nail plate, secondary bacterial infection, and pain from diabetes. The most beneficial way to reduce the likelihood of relapse is to combine treatments. Therapy for onychomycosis is a long road that does not always lead to complete recovery. However, do not forget that the effect of systemic therapy is up to 80%.
Prevention
Prevention includesa series of events, thanks to which you can significantly reduce the percentage of onychomycosis infection and reduce the likelihood of recurrence.
- Disinfection of personal and public items.
- Systematic disinfection of shoes.
- Treatment of feet, hands, folds with local antifungal agents with the recommendations of a dermatologist (under favorable conditions - favorite localization).
- If the diagnosis of onychomycosis is confirmed, it is necessary to visit the doctor for monitoring every 6 weeks and after the completion of systemic therapy.
- If possible, you should disinfect the nail plates at each visit to the doctor.
The result
Onychomycosis (nail 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, check all the skin and nails, and exclude other diseases that mimic onychomycosis. If there is any doubt about the diagnosis, it should be confirmed either by culture (preferably) or by histological examination of nail sections followed by staining.
Therapy includes surgical removal, local and general medications. Treatment of onychomycosis is a long process and can last 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 determine an individualized treatment plan.