The term onychomycosis (fungus of the toenails and fingernails) describes a fungal infection of the nail caused by dermatophytes, non-dermatophytic molds or yeasts. There are four clinically distinct forms of onychomycosis. Diagnosis is based on examination with CON, microscopy and histology. Most often, treatment includes systemic and local therapy, sometimes resorting to surgical removal.
Factors contributing to 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 onychomycosis of the toenails).
- Age. The incidence of the disease in humans increases with age. In 15-20% of the population, the pathology occurs at 40-60 years of age.
- Diseases of internal organs. Disruption of the nervous, endocrine (most often onychomycosis occurs in people with diabetes) or immune (immunosuppression, in particular HIV infection) systems.
- A large nail mass, which consists of a thick nail plate and the contents underneath it, can cause discomfort when wearing shoes.
- Traumatization. Constant trauma to the nail or injury and lack of proper treatment.
Prevalence of the disease
Onychomycosis– the most common nail disease, which is the cause of 50% of all cases of onychodystrophy (destruction of the nail plate). It affects up to 14% of the population, and both the prevalence of the disease in older people and the overall incidence are increasing. The incidence of onychomycosis in children and adolescents is also increasing; onychomycosis accounts for 20% of dermatophyte infections in children.
The increase in the prevalence of the disease may be associated with wearing tight shoes, an increase in the number of people taking immunosuppressive therapy, and the increasing use of public locker 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 on the toes have combined skin infections, most often tinea pedis (about 30%).
The causative agent of onychomycosis
In most cases, onychomycosis is caused by dermatophytes, with T. rubrum and T. interdigitale being the causative agents of infection in 90% of all cases. T. tonsurans and E. floccosum have also been documented as etiological agents.
Yeast and non-dermatophyte mold organisms such as Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis and Scytalidium are the source of onychomycosis of the toes in approximately 10% of cases. It is interesting to note that Candida species are the causative agents in 30% of cases of onychomycosis of the fingers, while non-dermatophytic molds are not found in the affected fingernails.
Pathogenesis
Dermatophytes have a wide range of enzymes that, acting as virulence factors, ensure adhesion of the pathogen to the nails. The first stage of infection is adhesion to keratin. Due to further decomposition of keratin and cascade release of mediators, an inflammatory reaction develops.
The stages of the pathogenesis of fungal infection are as follows.
Adhesion
Fungi overcome several lines of host defense before hyphae begin to 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 examined 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 has taken place, the spores germinate and move on to the next stage - invasion.
Invasion
Traumatization and maceration are a favorable environment for the penetration of fungi. The invasion of the germinating elements of the fungus ends with the release of various proteases and lipases, in general, various products that serve as nutrients for the fungi.
Owner's reaction
Fungi face multiple protective barriers in the host, such as inflammatory mediators, fatty acids, and cellular immunity. The first and most important barrier is keratinocytes, which are encountered by invading fungal elements. The role of keratinocytes: proliferation (to enhance the desquamation of horny scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As soon as the fungus penetrates deeper, more and more new nonspecific mechanisms are activated for protection.
The severity of the host's inflammatory response depends on the immune status, as well as on the natural habitat of the dermatophytes involved in the invasion. The next level of defense is a 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 indicating a genetic predisposition to fungal infection, there are no molecular proven studies.
Clinical picture and symptoms of damage to toenails and fingernails
There are four characteristic clinical forms of infection. These forms can be isolated or include 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. It begins with pathogen invasion in the stratum corneum of the hyponychium and distal nail bed, resulting in a whitish or brownish-yellow opacification of the distal end of the nail. The infection then spreads proximally up the nail bed to the ventral aspect of the nail plate.
Hyperproliferation or impaired differentiation in the nail bed as a result of response to infection causes subungual hyperkeratosis, while progressive invasion of the nail plate leads to increased nail dystrophy.
Proximal subungual onychomycosis
It occurs as a result of infection of the proximal nail fold, mainly by the organisms T. rubrum and T. megninii. Clinic: clouding of the proximal part of the nail with a white or beige tint. 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 examined for HIV infection, since this form is considered a marker of this disease.
White superficial onychomycosis
It occurs due to 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 known pathogens of this form. Candida species can invade the hyponychium of the epithelium and eventually infect the nail along the entire thickness of the nail plate.
Candidal onychomycosis
Damage to the nail plate caused by Candida albicans is observed exclusively in chronic mucocutaneous candidiasis (a rare disease). Usually all fingernails are affected. The nail plate thickens and acquires various shades of yellow-brown color.
Diagnosis of onychomycosis
Although onychomycosis accounts for 50% of cases of nail dystrophy, it is advisable to obtain laboratory confirmation of the diagnosis before starting toxic systemic antifungal drugs.
Study of subungual masses with KOH, cultural analysis of the material of the nail plate and subungual masses on Sabouraud dextrose agar (with and without antimicrobial additives) and staining of nail clippings using the PAS method are the most informative methods.
Study with CON
It is a standard test for suspected onychomycosis. However, quite often it gives a negative result even with a high index of clinical suspicion, and cultural analysis of the nail material in which hyphae were found during the study 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 sampling.
Cultural analysis
This laboratory test determines the type of fungus and determines the presence of dermatophytes (organisms that respond to antifungal medications).
To distinguish pathogens from contaminants, the following recommendations are offered:
- if the dermatophyte is isolated in culture, it is considered a pathogen;
- Nondermatophytic mold or yeast organisms isolated in culture are relevant only if hyphae, spores, or yeast cells are observed under a microscope and recurrent active growth of the nondermatophytic mold pathogen is observed without isolation.
Cultural analysis, PAS - the method of staining nail clippings is the most sensitive and does not require waiting for results for several weeks.
Pathohistological examination
During pathohistological examination, the 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 microorganisms are found superficially on the back of the nail, displaying a pattern of their unique "perforating organs" and modified hyphal elements called "bitten leaves. "With candidal onychomycosis, invasion of pseudohyphae is observed. Histological examination of onychomycosis occurs with special dyes.
Differential diagnosis of onychomycosis
| Most likely | Sometimes probable | Rarely found |
|---|---|---|
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Melanoma |
Treatment methods for nail fungus
Treatment for 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, especially against the background of diabetes mellitus, it is imperative to prescribe therapy.
Topical antifungal drugs
In patients with distal nail involvement or contraindications for systemic therapy, local therapy is recommended. However, we must remember that only local therapy with antifungal agents is not effective enough.
A varnish from the oxypyridone group is gaining increasing popularity, which is applied daily for 49 weeks, mycological cure is achieved in about 40% of patients, and nail cleansing (clinical cure) in 5% of cases of mild or moderate onychomycosis caused by dermatophytes.
Despite its much lower effectiveness compared to systemic antifungal drugs, local use of the drug avoids the risk of drug-drug interactions.
Another drug, specially developed in the form of nail polish, is used 2 times a week. It is a representative of a new class of antifungal drugs, morpholine derivatives, active against yeasts, dermatophytes and molds that cause onychomycosis.
This product may have higher mycological cure rates compared to the previous varnish; however, controlled studies are needed to determine a statistically significant difference.
Antifungal drugs for oral administration
A systemic antifungal drug is needed in cases of onychomycosis involving the matrix area, or if a shorter course of treatment or a higher chance of clearance and cure is desired. When choosing an antifungal drug, one should first take into account the etiology of the pathogen, potential side effects and the risk of drug interactions 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 shows variable effectiveness against Candida species.
A standard dose of 6 weeks is effective for most toenail injections, while a minimum of 12 weeks is required for toenail injections. Most side effects are related to digestive system 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 toenail onychomycosis. The clinical cure rate in various studies is approximately 50%, although treatment rates are higher in patients over 65 years of age.
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 daily pulse dosing for one week per month 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. therapy for lesions of toenails.
In children, the drug is dosed individually depending on weight. Although the drug has a broader spectrum of action than its predecessor, studies have shown a significantly lower cure rate with it and a higher relapse rate.
Elevated liver enzyme levels occur in less than 0. 5% of patients during therapy and return to normal within 12 weeks after cessation of treatment.
A drug that acts fungistatically against dermatophytes, some non-dermatophytic molds and Candida species. This medication 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. It makes sense to have a complete blood count and liver function tests done 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 therapy regimens may produce higher clearance rates than systemic or topical therapy alone. Ingestion of an allylamine drug in combination with the application of a morpholine varnish results in clinical cure and a negative mycological test result in approximately 60% of patients, compared with 45% of patients receiving only a systemic allylamine antifungal drug. However, another study showed no additional benefit when combining a systemic allylamine agent with a solution of an oxypyridone drug.
Other drugs
Fungicidal activity shown in vitro for thymol, camphor, menthol and Eucalyptus citriodora oil indicates 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 cure in isolated cases.
Surgery
Final treatment options for treatment-resistant cases include surgical removal of the nail with urea. To remove more of the crumbling masses from the affected nail, special nippers are used.
Many doctors believe that the main and first method of treating nail fungus is mechanical removal of the nail. Most often, surgical removal of the affected nail is recommended, and less often, removal using keratolytic patches.
Traditional methods in the fight against nail fungus
Despite the large number of different folk recipes for removing nail fungus, dermatologists do not recommend choosing this treatment option and starting with a "home diagnosis. "It is wiser to start therapy with local drugs that have undergone clinical trials and proven effective.
Course and prognosis
Poor prognostic signs are pain that appears due to thickening of the nail plate, the addition of a secondary bacterial infection, and diabetes mellitus. The most beneficial way to reduce the likelihood of relapse is to combine treatment methods. Therapy for onychomycosis is a long path 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 number of events, thanks to which you can significantly reduce the percentage of onychomycosis infection and reduce the likelihood of relapse.
- Disinfection of personal and public items.
- Systematic disinfection of shoes.
- Treatment of feet, hands, folds (under favorable conditions - favorite localization) with local antifungal agents with the recommendations of a dermatologist.
- If the diagnosis of onychomycosis is confirmed, it is necessary to visit a doctor for monitoring every 6 weeks and upon completion of systemic therapy.
- If possible, at each visit to the doctor you should sanitize the nail plates.
Conclusion
Onychomycosis (fungus of the fingernails and toenails) 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 also exclude other diseases that mimic onychomycosis. If there is any doubt about the diagnosis, it must be confirmed either by culture (most preferably) or by histological examination of nail clippings followed by staining.
Therapy includes surgical removal, local and general medications. Treatment of onychomycosis is a long process that can last for several years, so you should not expect recovery "from one pill. "If you suspect nail fungus, consult a specialist to confirm the diagnosis and prescribe an individual treatment plan.