The term onychomycosis (toenail and fingernail fungus) describes a fungal infection of the nail caused by dermatophytes, nondermatophyte molds, or yeasts. There are four clinically distinct forms of onychomycosis. The diagnosis is based on CON examination, microscopy and histology. Most often, treatment includes systemic and local therapy, sometimes resorting to surgical removal.
Factors contributing to nail mycosis
- Increased sweating (hyperhidrosis).
- Vascular insufficiency. Violation of the structure and tone of the veins, especially of 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 manifests itself between the ages of 40 and 60.
- Diseases of the internal organs. Destruction of the nervous, endocrine (most often onychomycosis occurs in people with diabetes) or immune systems (immunosuppression, especially HIV infection).
- A large nail mass, consisting of a thick nail plate and underlying contents, can cause discomfort when wearing shoes.
- Traumatization. Constant trauma to the nail or injury and lack of adequate 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 the elderly and the overall incidence are increasing. The incidence of onychomycosis in children and adolescents is also increasing; onychomycosis represent 20% of dermatophyte infections in children.
The increased prevalence of the disease may be associated with the use of tight shoes, the increase in the number of people taking immunosuppressive therapies and the increasing 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 spillover or spread of the infection to other areas. Up to 40% of patients with onychomycosis of 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 the 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 cause of onychomycosis of the toes in about 10% of cases. Interestingly, Candida species are the causative agents in 30% of cases of finger onychomycosis, while no nondermatophytic molds are present in the affected nails.
Pathogenesis
Dermatophytes possess a wide range of enzymes which, acting as virulence factors, ensure the adhesion of the pathogen to the nails. The first stage of infection is adhesion to keratin. Due to 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.
Membership
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 and competitive bacterial colonization.
Numerous recent studies have examined the molecular mechanisms involved in the adhesion of arthroconidia to keratinized surfaces. Dermatophytes have been shown to selectively utilize their proteolytic reserves during adhesion and invasion. Some time after attachment, the spores germinate and move on to the next stage: invasion.
Invasion
Traumatization and maceration constitute a favorable environment for the penetration of fungi. The invasion of the germinal elements of the fungus ends with the release of various proteases and lipases, in general of various products that serve as nourishment 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 encounter the invading fungal elements. The role of keratinocytes: proliferation (to promote desquamation of the horny scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As the fungus penetrates deeper, more and more new non-specific protection 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 infections.
Although epidemiological observations indicate a genetic predisposition to fungal infections, there are no proven molecular 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 the invasion of pathogens into the stratum corneum of the hyponychium and the distal nail bed, resulting in a whitish or yellow-brownish clouding of the distal end of the nail. The infection then spreads proximally along the nail bed to the ventral part of the nail plate.
Hyperproliferation or reduced differentiation 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 occurs following infection of the proximal nail fold, primarily by the organisms T. rubrum and T. megninii. Clinical: dullness of the proximal part of the nail with a white or beige tint. This opacification gradually increases and involves the entire nail, ultimately leading to leukonychia, proximal onycholysis, and/or destruction of the entire nail.
Patients with proximal subungual onychomycosis should be examined 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 nail. 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.
Candida onychomycosis
Damage to the nail plate caused by Candida albicans is seen exclusively in chronic mucocutaneous candidiasis (a rare disease). Usually all nails are affected. The nail plate thickens and acquires various shades of yellow-brown color.
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 medications.
The study of subungual masses with KOH, culture analysis of nail plate material 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, it very often gives a negative result even with a high index of clinical suspicion, and culture 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 error 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 drugs).
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 only relevant if hyphae, spores, or yeast cells are observed under the 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 histopathological 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 found superficially on the back of the nail, showing a pattern of their unique "piercing organs" and modified hyphal elements called "bitten leaves". With candidal onychomycosis, invasion of the pseudohyphae is observed. Histological examination of onychomycosis occurs with special dyes.
Differential diagnosis of onychomycosis
| More 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. In combination 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 to systemic therapy, local therapy is recommended. However, we must remember that only local therapy with antifungal agents is not sufficiently effective.
A varnish from the oxypyridone group is gaining more and more popularity, which is applied daily for 49 weeks, mycological healing is achieved in about 40% of patients, and nail cleaning (clinical cure) in 5% of cases of mild onychomycosis or moderate caused by dermatophytes.
Despite its much lower efficacy than 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, morpholine derivatives, active against yeasts, dermatophytes and molds that cause onychomycosis.
This product may have higher mycological cure rates than the previous paint; however, controlled studies are needed to determine a statistically significant difference.
Antifungal drugs for oral administration
A systemic antifungal drug is necessary in cases of onychomycosis involving the matrix area or if a shorter course of treatment or a greater chance of resolution 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 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. The clinical cure rate in various studies is approximately 50%, although treatment 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 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 courses of therapy for nails and at least three months or three pulses of therapy for toenail lesions .
In children, the drug 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 with it.
Elevated liver enzyme levels occur in less than 0. 5% of patients during therapy and return to normal within 12 weeks of stopping treatment.
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-mentioned drugs. A complete blood count and liver function tests should be performed before treatment and 6 weeks after starting treatment.
A drug from the Grisan group is no longer considered standard therapy for onychomycosis due to the long treatment course, potential side effects, drug interactions, and relatively low cure rates.
Combination treatment 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 to 45% of patients receiving an allylamine antifungal drug alone systemic. However, another study showed no additional benefit when combining a systemic allylamine agent with an oxypyridone drug solution.
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 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 healing 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 forceps 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 often, removal with 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 undergone clinical trials and proven effective.
Course and prognosis
Unfavorable 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 recurrence is to combine treatment methods. Therapy for onychomycosis 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 includesa series of events, thanks to which it is possible to significantly reduce the rate of onychomycosis infection and reduce the likelihood of recurrence.
- Disinfection of personal and public objects.
- Systematic disinfection of shoes.
- Treatment of feet, hands, folds (under favorable conditions - preferred localization) with local antifungal agents with the recommendations of a dermatologist.
- If the diagnosis of onychomycosis is confirmed, you should visit a doctor for monitoring every 6 weeks and at the end of systemic therapy.
- If possible, at each visit to the doctor you should disinfect your nails.
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 also exclude other diseases that mimic onychomycosis. If there is any doubt about the diagnosis, it should be confirmed by culture (preferably) or histological examination of nail clippings followed by staining.
Treatment includes surgical removal and local and general medications. Treatment of onychomycosis is a long process that can last 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.