The term onychomycosis (fingernail and toenail fungus) describes a fungal infection of the nail caused by dermatophytes, nondermatophytic 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 that contribute 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 for onychomycosis of the toenails).
- Age. The incidence of the disease in humans increases with age. In 15-20% of the population, the pathology occurs between 40 and 60 years of age.
- Diseases of internal organs. Disturbance of the nervous, endocrine (onychomycosis occurs more frequently in people with diabetes) or immunological systems (immunosuppression, in particular HIV infection).
- A large nail mass, consisting of a thick nail plate and the contents under it, can cause discomfort when wearing shoes.
- Traumatization. Constant trauma to the nail or injury and lack of adequate treatment.
Disease prevalence
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 represents 20% of dermatophyte infections in children.
The increased prevalence of the disease may be associated with the wearing of 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 toe onychomycosis 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 cases. T. tonsurans and E. floccosum have also been documented as etiological agents.
Non-dermatophyte yeasts and molds such as Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis and Scytalidium are the source of toe onychomycosis 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 nondermatophytic molds are not found in affected nails.
Pathogenesis
Dermatophytes possess a wide range of enzymes that, acting as virulence factors, ensure the adhesion of the pathogen to the nails. The first stage of infection is adhesion to the keratin. Due to further breakdown of keratin and the cascade release of mediators, an inflammatory reaction develops.
The stages of the pathogenesis of fungal infection are as follows.
Accession
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. Nonspecific first 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 occurred, the spores germinate and move on to the next stage: invasion.
Invasion
Traumatization and maceration are a favorable environment for fungal penetration. The invasion of the germinative elements of the fungus ends with the release of various proteases and lipases, in general, various products that serve as nutrients for the fungi.
The 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 the keratinocytes, which are confronted by invading fungal elements. The role of keratinocytes: proliferation (to improve the peeling of horny scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As soon as the fungus penetrates deeper, more and more non-specific protective mechanisms are activated.
The severity of the host's inflammatory response depends on the immune status as well as the natural habitat of the dermatophytes involved in the invasion. The next level of defense is a delayed-type hypersensitivity reaction, 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 proven molecular studies.
Clinical picture and symptoms of damage to the nails of the feet and hands.
There are four characteristic clinical forms of infection. These forms may 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 the invasion of pathogens into the stratum corneum of the hyponychium and the distal nail bed, resulting in a whitish or brownish-yellow opacification of the distal end of the nail. The infection then spreads proximally through the nail bed to the ventral aspect of the nail plate.
Hyperproliferation or impaired differentiation in 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 occurs as a result of an infection of the proximal nail fold, mainly by the organisms T. rubrum and T. megninii. Clinic: opacity of the proximal part of the nail with a white or beige tint. This opacification gradually increases and affects the entire nail, eventually causing 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 of this disease.
White superficial onychomycosis
It occurs due to direct invasion of the dorsal nail plate and appears as well-defined white or dull yellow 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 in this form. Candida species can invade the hyponychium of the epithelium and eventually infect the nail throughout the thickness of the nail plate.
Onychomycosis candidiasis
Damage to the nail plate caused by Candida albicans is observed exclusively in chronic mucocutaneous candidiasis (a rare disease). Usually all nails are affected. The nail plate thickens and acquires various shades of yellow-brown.
Diagnosis of onychomycosis.
Although onychomycosis accounts for 50% of nail dystrophy cases, it is advisable to obtain laboratory confirmation of the diagnosis before initiating toxic systemic antifungal drugs.
The most informative methods are the 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.
Study with CON
It is a standard test for suspected onychomycosis. However, very 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 usually 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 pathogenic;
- Non-dermatophytic molds 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 non-dermatophytic 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 the results for several weeks.
Pathohistological examination
During pathohistological examination, hyphae are located between the layers of the nail plate, parallel to the surface. Focal spongiosis and parakeratosis, as well as an inflammatory reaction, can be observed in the epidermis.
In superficial white onychomycosis, the microorganisms are located superficially on the back of the nail, showing a pattern of their unique "perforating organs" and modified hyphal elements called "bitten leaves. "With Candida onychomycosis, pseudohyphal invasion is seen. Histological examination of onychomycosis is performed with special dyes.
Differential diagnosis of onychomycosis.
| Most likely | Sometimes probable | rarely found |
|---|---|---|
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Melanoma |
Treatment methods for nail fungus.
Treatment of nail fungus depends on the severity of the nail lesion, the presence of associated tinea pedis, and the effectiveness and possible side effects of the treatment regimen. If the nail involvement is minimal, localized treatment 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 medications
In patients with distal nail involvement or contraindications to systemic therapy, local therapy is recommended. However, we must remember that local therapy with antifungal agents alone is not effective enough.
A varnish from the oxypyridone group is becoming increasingly popular, which is applied daily for 49 weeks, mycological cure is achieved in approximately 40% of patients and nail cleaning (clinical cure) is achieved in 5% of patients. cases of mild or moderate onychomycosis caused by dermatophytes. .
Despite its much lower efficacy compared to systemic antifungal drugs, topical use of the drug avoids the risk of 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, derivatives of morpholine, 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 medications for oral administration.
A systemic antifungal drug is needed in cases of onychomycosis affecting the womb area, or if a shorter treatment or greater chance of clearance and cure is desired. When choosing an antifungal drug, one must first take into account the etiology of the pathogen, possible side effects, and the risk of drug interactions in each individual patient.
A drug from the group of allylamines, which has a fungistatic and fungicidal effect against dermatophytes, Aspergillus, is less effective against Scopulariopsis. The product is not recommended for Candida onychomycosis because it shows variable efficacy against Candida species.
A standard 6-week dosage 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, such as diarrhea, nausea, changes in taste, 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 several studies is approximately 50%, although treatment rates are higher in patients over 65 years of age.
Medication from the azole group that has a fungistatic effect against dermatophytes, as well as against non-dermatophyte molds and yeasts. Safe and effective regimens include daily pulse dosing for one week a 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 of therapy for nail lesions. the toenails.
In children, the medication is dosed individually based on weight. Although the drug has a broader spectrum of action than its predecessor, studies have shown a significantly lower cure rate and a higher relapse rate.
Elevated liver enzyme levels occur in less than 0. 5% of patients during treatment and return to normal within 12 weeks of stopping treatment.
Medication 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 medications. It makes sense to have a complete blood count and liver function tests 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 treatment, possible side effects, 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 application of a morpholine varnish produces clinical cure and a negative mycological test in approximately 60% of patients, compared with 45% of patients receiving an allylamine antifungal drug alone. Systemic allylamine. However, another study showed no additional benefit from combining a systemic allylamine agent with a solution of an oxypyridone drug.
Other drugs
The fungicidal activity demonstrated in vitro for thymol, camphor, menthol and eucalyptus citriodora oil indicates the potential for additional therapeutic strategies in the treatment of onychomycosis. An alcoholic solution of thymol can be used in the form of drops on the nail plate and hyponychia. The use of topical preparations with thymol for nails produces healing in isolated cases.
Surgery
Final treatment options for refractory cases include surgical removal of the nail with urea. To remove further crumbly masses from the affected nail, special tweezers are used.
Many doctors believe that the main and first method of treating nail fungus is mechanical removal of the nail. In most cases, surgical removal of the affected nail is recommended, and less frequently, removal with keratolytic patches.
Traditional methods in the fight against nail fungus.
Despite the large number of different folk recipes for eliminating 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 have proven their effectiveness.
Course and forecast
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 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 it is possible to significantly reduce the percentage of onychomycosis infection and reduce the probability of relapse.
- Disinfection of personal and public objects.
- Systematic disinfection of shoes.
- Treatment of feet, hands, folds (in favorable conditions, favorite localization) with local antifungal agents according to 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, the nail plates should be disinfected at each visit to the doctor.
Conclusion
Onychomycosis (fingernail and toenail fungus) is an infection caused by several fungi. This disease affects the nail plate of the fingers or toes. When making a diagnosis, the entire skin and nails are examined, and other diseases that mimic onychomycosis are also excluded. If there is any doubt about the diagnosis, it should be confirmed by culture (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 several years, so one should not expect recovery "with a single pill. "If you suspect nail fungus, consult a specialist to confirm the diagnosis and prescribe an individual treatment plan.