The term onychomycosis (fingernail fungus) describes a fungal infection of the nail caused by dermatophytes, non-dermatophyte fungi, or yeast. 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 in 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, pathology occurs at 40-60 years of age.
- Diseases of internal organs. Disturbance 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 beneath it, can cause discomfort when wearing shoes.
- Traumatization. Trauma or constant injury to the nail 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 global incidence are increasing. The incidence of onychomycosis in children and adolescents is also increasing; Onychomycosis is responsible for 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 on immunosuppressive therapy and the increasing use of public changing rooms.
Nail disease often begins with tinea pedis before spreading to the nail bed, where eradication is difficult. This area serves as a reservoir for local recurrences or spread of 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 all cases. T. tonsurans and E. floccosum have also been documented as etiological agents.
Yeasts and non-dermatophyte 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 of 30% of cases of onychomycosis of the fingers, while non-dermatophyte fungi are not found in affected nails.
Pathogenesis
Dermatophytes have 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 keratin. Due to the greater decomposition of keratin and the cascade release of mediators, an inflammatory reaction develops.
The stages of 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. The first 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, the spores germinate and move on to the next stage - invasion.
Invasion
Traumatization and maceration are favorable environments for the penetration of fungi. The invasion of the fungus' germinative elements ends with the release of several proteases and lipases, in general, several products that serve as nutrients for the fungi.
Owner reaction
Fungi face multiple protective barriers in the host, such as inflammatory mediators, fatty acids and cellular immunity. The first and most important barrier are keratinocytes, which are encountered by invading fungal elements. The role of keratinocytes: proliferation (to increase the desquamation of horny scales), secretion of antimicrobial peptides, anti-inflammatory cytokines. As the fungus penetrates deeper, more and more nonspecific 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.
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 the pathogen into the stratum corneum of the hyponychium and the distal nail bed, resulting in a whitish or yellow-brown opacification of the distal end of the nail. The infection then spreads proximally across the nail bed to the ventral surface 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. Clinical: clouding of the proximal part of the nail with a white or beige hue. 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 of this disease.
White superficial onychomycosis
It occurs due to direct invasion of the dorsal nail plate and appears as dull, well-defined white or yellow spots on the surface of the nail. The pathogens are usually T. interdigitale and T. mentargophytes, although non-dermatophyte fungi such as Aspergillus, Fusarium and Scopulariopsis are also known pathogens in 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). Generally 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, cultural 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 often 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 CON study 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 medications).
To distinguish pathogens from contaminants, the following recommendations are offered:
- if the dermatophyte is isolated in culture, it is considered a pathogen;
- Non-dermatophyte fungi 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 non-dermatophyte fungal pathogen is observed without isolation.
Cultural analysis, PAS - the nail clipping staining method is the most sensitive and does not require waiting for results for several weeks.
Pathological examination
During the anatomopathological examination, the hyphae are located between the layers of the nail plate, parallel to the surface. Focal spongiosis and parakeratosis can be observed in the epidermis, in addition to 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. "In Candida onychomycosis, pseudohyphae invasion is observed. Histological examination of onychomycosis takes place using special dyes.
Differential diagnosis of onychomycosis
| Probably | Sometimes likely | Rarely found |
|---|---|---|
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Melanoma |
Treatment methods for nail fungus
Treatment of nail fungus depends on the severity of the nail injury, 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 essential 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 gaining more and more popularity, which is applied daily for 49 weeks, mycological cure is achieved in around 40% of patients and nail cleaning (clinical cure) in 5% of cases of mild or mild onychomycosis. moderate caused by dermatophytes.
Despite its much lower effectiveness compared to systemic antifungals, local use of the medication avoids the risk of drug interactions.
Another medicine, specially developed in the form of nail polish, is used 2 times a week. It is representative of a new class of antifungals, derived from morpholine, active against yeasts, dermatophytes and fungi 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 medication is necessary in cases of onychomycosis involving the matrix area, or if shorter treatment or a greater chance of elimination and cure is desired. When choosing an antifungal medication, one must first take into account the etiology of the pathogen, potential side effects and the risk of drug interactions in each 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 Candida onychomycosis because it has 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, 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.
Medicine from the azoles group that has a fungistatic effect against dermatophytes, as well as non-dermatophyte fungi and yeasts. 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 nail therapy and at least three months or three pulses.
In children, the medicine is administered individually depending 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 therapy and return to normal within 12 weeks after stopping treatment.
Medication 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 medications. It makes sense to perform 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 standard therapy for onychomycosis due to the long course of treatment, potential 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 medication in combination with 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 only a systemic allylamine antifungal medication. However, another study showed no additional benefit when combining a systemic allylamine agent with a solution of an oxypyridone medication.
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 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 crumbling 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. Most often, surgical removal of the affected nail is recommended and, less frequently, removal with keratolytic adhesives.
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 "home diagnosis". It is wiser to start therapy with local medicines that have undergone clinical trials and have been proven to be effective.
Course and prognosis
Signs of poor prognosis are pain that appears due to thickening of the nail plate, 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 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 - preferred location) with local antifungals with the recommendation of a dermatologist.
- If the diagnosis of onychomycosis is confirmed, a medical consultation is required for follow-up every 6 weeks and after the end of systemic therapy.
- If possible, at each visit to the doctor, you should clean your nail plates.
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 the diagnosis, examine the entire skin and nails, in addition to excluding other diseases that simulate onychomycosis. 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 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.