The term onychomycosis (toenail and fingernail fungus) describes a fungal nail infection caused by dermatophytes, non-dermatophyte fungi, 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 toenail onychomycosis).
- Age. 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 years.
- Diseases of internal organs. Disorder of the nervous, endocrine (onychomycosis more often occurs in people with diabetes) or immune (immunosuppression, especially HIV infection).
- A large nail mass, which consists of a thick nail plate and the contents below it, can cause discomfort when wearing shoes.
- Traumatization. Persistent nail trauma or injury and lack of proper 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 the elderly 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 increased prevalence of the disease may be associated with wearing tight shoes, an increase in the number of people receiving immunosuppressive therapy, and increased 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, where the causative agents of infection are T. rubrum and T. interdigitale in 90% of all cases. T. tonsurans and E. floccosum have also been documented as etiological agents.
Yeast and non-dermatophyte fungal organisms such as Acremonium, Aspergillus, Fusarium, Scopulariopsis brevicaulis and Scytalidium are the source of onychomycosis of the fingers in approximately 10% of cases. It is interesting to note that Candida species are the causative agents in 30% of cases of toenail onychomycosis, while non-dermatophytic fungi are not found in affected nails.
Pathogenesis
Dermatophytes have a wide range of enzymes that, acting as virulence factors, ensure attachment of the pathogen to the nail. The first stage of infection is attachment to keratin. Due to the further decomposition of keratin and the cascade release of mediators, an inflammatory reaction develops.
The stages of the pathogenesis of fungal infection are as follows.
Ascent
The fungus overcomes several lines of host defense before the hyphae begin to survive in keratinized tissue. The first is the successful attachment 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 arthroconids to keratinized surfaces. Dermatophytes have been shown to selectively use their proteolytic reserves during attachment and invasion. Some time after attachment has occurred, the spores germinate and move to the next stage - invasion.
The invasion
Traumatization and maceration are a favorable environment for the penetration of fungi. The invasion of the germinating elements of the fungi ends with the release of various proteases and lipases, generally of various products that serve as nutrients for the fungi.
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Fungi face multiple defense 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 increase desquamation of horny scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As the fungus penetrates deeper, more and more new non-specific defense 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, 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 proven molecular studies.
Clinical appearance and symptoms of damage to the toenails and nails
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 the invasion of the pathogen into the stratum corneum of the hyponychium and the distal nail bed, resulting in a white or yellow-brown darkening of the distal edge of the nail. The infection then spreads close to the nail bed on 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 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 shade. This darkening gradually increases to involve 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 of this disease.
Superficial white onychomycosis
It occurs due to direct invasion of the dorsal nail plate and appears as white or pale yellow, well-defined spots on the surface of the toenail. The pathogens are usually T. interdigitale and T. mentargophytes, although non-dermatophyte fungi 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 throughout 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). All nails are usually 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 obtain laboratory confirmation of the diagnosis before starting toxic systemic antifungal drugs.
The study of subungual masses with KOH, cultural analysis of the material of the nail plate and subungual masses in Sabouraud dextrose agar (with and without antimicrobial additives) and staining of nail sections with the PAS method are the most informative methods.
Study with CON
It is a standard test for suspected onychomycosis. However, it quite often gives a negative result even with a high index of clinical suspicion, and the cultural analysis of 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 the 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;
- Nondermatophytic mold or yeast organisms isolated in culture are significant only if hyphae, spores, or yeast cells are observed under a microscope and active recurrent growth of the nondermatophytic mold pathogen is observed without isolation.
Cultural analysis, PAS - the method of staining nail clippings is more 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, focal spongiosis and parakeratosis can be observed, as well as an inflammatory reaction.
In superficial white onychomycosis, the microorganisms are found superficially on the back of the nail, displaying a pattern of their unique "piercing organs" and modified hyphal elements called "bitten leaves. "With candidal onychomycosis, the invasion of pseudohyphae is observed. Histological examination of onychomycosis occurs with special colors.
Differential diagnosis of onychomycosis
| Most likely | Sometimes possible | It is 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 necessary to prescribe therapy.
Topical antifungal medications
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 spray from the oxypyridone group is gaining more and more popularity, which is applied daily for 49 weeks, mycological cure is achieved in about 40% of patients and nail clearance (clinical cure) in 5% of cases of mild onychomycosis ormoderate caused by dermatophytes. .
Despite its much lower effectiveness compared to systemic antifungal drugs, the local 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, morpholine derivatives, active against yeasts, dermatophytes and fungi that cause onychomycosis.
This product may have a higher rate of mycological cure compared to the previous varnish; however, controlled studies are needed to determine a statistically significant difference.
Antifungal drugs for oral administration
A systemic antifungal medication is necessary 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, the etiology of the pathogen, possible side effects and the risk of drug interactions in each individual patient should be taken into account.
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 efficacy 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. Clinical cure rates in various studies are approximately 50%, although cure 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 against 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 fingernail therapy and at least three months or three pulses. therapy for toenail lesions.
In 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 a significantly lower cure rate with it and a higher relapse rate.
Elevated levels of liver enzymes occur in less than 0. 5% of patients during therapy and return to normal within 12 weeks after discontinuation of treatment.
A drug that acts fungistatically against dermatophytes, some non-dermatophyte fungi 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 is reasonable 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, possible side effects, drug interactions, and the relatively low cure rate.
Combination therapy regimens may produce higher clearance rates than systemic or topical therapy alone. Ingestion of an allylamine medication in combination with application of a morpholine spray results in clinical cure and a negative mycological test result in approximately 60% of patients, compared with 45% of patients receiving a systemic allylamine antifungal medication alone. However, another study showed no additional benefit when combining a systemic allylamine agent with an oxypyridone drug solution.
Other drugs
The fungicidal activity shown in vitro for thymol, camphor, menthol and oil of Eucalyptus citriodora shows 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 hyponicia. The use of local preparations with thymol for the nails leads to healing in isolated cases.
Surgery
Final treatment options for treatment-resistant cases include surgical removal of the urea nail. To remove more of the crushed masses from the affected nails, special suckers are used.
Many doctors believe that the main and first method of treating nail fungus is the mechanical removal of the nails. Surgical removal of the affected nail is most often recommended, and less often removal using keratolytic patches.
Traditional methods in the fight against nail fungus
Despite the large number of different popular 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 passed clinical trials and have been proven effective.
Course and prognosis
Bad prognostic signs are pain that occurs due to thickening of the nail plate, the addition of a secondary bacterial infection and diabetes mellitus. The most useful 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%.
Preventing
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 (under favorable conditions - preferred localization) with local antifungal agents with the dermatologist's recommendations.
- If the diagnosis of onychomycosis is confirmed, it is necessary to visit a doctor for monitoring every 6 weeks and after the end of systemic therapy.
- If possible, you should disinfect the nail plates at every visit to the doctor.
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 the entire skin and nails, and also exclude other diseases that mimic onychomycosis. If there is any doubt about the diagnosis, it should be confirmed either by culture (preferred) 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 that can last for several years, so you should not expect a cure "from a pill". If you suspect nail fungus, consult a specialist to confirm the diagnosis and prescribe an individual treatment plan.