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Onychomycosis: causes, symptoms, diagnosis, treatment
Last reviewed: 05.07.2025
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What causes onychomycosis?
Approximately 10% of the population suffers from onychomycosis. The risk group includes patients with dermatomycosis of the soles, nail dystrophy, circulatory disorders and the elderly. Toenails are infected 10 times more often than fingernails. Approximately 60-80% of cases are caused by dermatophytes (for example, Trichophyton rubrum). In the remaining cases, the infection is caused by Aspergillus, Scopulariopsis, Fusarium. Patients with chronic cutaneous mucosal candidiasis may develop candidal onychomycosis (more common on the hands).
Currently, yeast-like fungi of the genus Candida and mold fungi, as well as mixed fungal infections, are becoming increasingly important in the etiology of onychomycosis.
Isolated infection of nail plates by fungi is rare. Usually, nail damage occurs secondarily when the fungus spreads from the affected skin of the finger, for example, with mycosis of the feet, hands. Hematogenous introduction of the fungus into the nail matrix area is also possible.
This type of onychomycosis occurs with trauma to the nail phalanx, as well as in patients with endocrine diseases, immunodeficiency states, in particular, with long-term treatment with glucocorticosteroids, cytostatics, HIV infection, etc. In the pathogenesis of onychomycosis, circulatory disorders in the extremities, especially the lower ones (varicose veins, obliterating endarteritis, heart failure with valve defects and hypertension) are of great importance. Functional and organic diseases of the nervous system, leading to impaired tissue trophism, are also important. In recent years, the number of young patients with angiotrophoneurosis, in particular the Raynaud's symptom complex, as a pathogenetic basis for the development of onychomycosis has increased. Given the systemic manifestations of the Raynaud phenomenon, widespread fungal infections of the nails are often encountered, usually with damage to the nail plates of the hands. Factors predisposing to onychomycosis include endocrine diseases (exogenous and endogenous hypercorticism, diabetes, disorders of the function of the sex glands), immunodeficiency (taking corticosteroids, cytostatic drugs, immunosuppressants, HIV infection), some chronic skin diseases characterized by disorders of cornification and dystrophy of the nail plates (ichthyosis, keratoderma, lichen planus). Among exogenous causes, an important role is played by injuries to the nail plates and distal parts of the extremities - mechanical, chemical (professional and domestic), as well as frostbite and perniosis. Trauma not only contributes to the penetration of the fungus into the nail plate, but often provokes the development of onychomycosis in people already infected with fungi. Thus, trauma to the nail fold during manicure and pedicure contributes to the development of onychomycosis of the hands in people with mycosis and onychomycosis of the feet.
Symptoms of onychomycosis
In onychomycosis, the nail plates of the feet are most often involved in the process, and less often - the hands. Usually, the lesion begins with the first and fifth toes. The main clinical signs of onychomycosis are changes in the color, shape of the nail due to subungual hyperkeratosis and destruction of the nail plate. In onychomycosis caused by dermatophytes or mixed microflora, the nail fold, as a rule, is not affected.
Depending on the dominant clinical symptom, three clinical forms of onychomycosis are distinguished: hypertrophic, normotrophic and atrophic.
In the hypertrophic form, the nail plate thickens due to subungual hyperkeratosis and acquires a yellowish color. At the same time, the surface of the nail may remain smooth for a long time. Later, the nail plate may separate from the nail bed, it loses its shine, and its edges become jagged.
In the normotrophic form of the lesion, there are yellowish and white areas in the thickness of the nail, while the nail plate does not change its shape, subungual hyperkeratosis is not expressed.
The atrophic form of onychomycosis is characterized by significant thinning, detachment of the nail plate from the nail bed, the formation of voids or its partial destruction.
In European and American dermatology, the most common classification of onychomycosis takes into account not only the clinical features of the affected nail plate, but also the variants of fungal penetration into it. Distal, distal-lateral, white superficial, proximal subungual and total dystrophic onychomycosis are distinguished.
Distal and distal-lateral subungual onychomycosis is the most common form of onychomycosis, in 85% of cases it is caused by Trichophyton rubrum. In this form, the pathogen usually enters the nail from the affected skin of the feet. The nail plate is infected from the free edge, usually after the nail bed is affected, the pathological process slowly spreads towards the matrix in the form of a splinter or a yellow oval spot. This form may be accompanied by the appearance of subungual hyperkeratosis.
White superficial onychomycosis is most often caused by Trichophyton mentagrophytes (approximately 90% of cases), less often it is associated with mold fungi of the genus Aspergillus. In white superficial onychomycosis, the nail plates of the first fingers are usually involved in the process. The prerequisite for the development of this form of onychomycosis is the softening of the nail plate in a humid environment, while the pathogen is localized superficially, the matrix and nail bed are not involved. This clinical form is characterized by superficial white lesions on the nail plate, resembling ordinary leukonychia.
Proximal subungual onychomycosis, like white superficial, is rare. It occurs as a result of the pathogen entering from the periungual fold or surrounding skin or, which is even rarer, develops against the background of white superficial onychomycosis. This form is characterized by the onset of the disease from the proximal part of the nail plate and rapid involvement of the nail matrix. Clinically, with proximal onychomycosis, areas of discoloration of the lunula of the nail plate first appear, after which onycholysis (separation of the nail from the nail bed) can appear quite quickly.
Total dystrophic onychomycosis develops against the background of distal or distal-lateral, less often proximal onychomycosis. This type occurs both with damage by dermatophytes and mold fungi, and yeast of the genus Candida. During examination, involvement of the entire nail plate is recorded, often with its partial or complete destruction.
Diagnosis of onychomycosis
Evaluation of clinical manifestations in nail plate diseases in onychodystrophies is important both in the diagnosis of various skin diseases and somatic pathology. Correct interpretation of the dermatological status, including the state of the nail plates, determines the direction of diagnostic search in various fields of medicine. It is this fact that increases the importance of assessing the condition of the nails not only for the purpose of diagnosing a particular disease, but also for the purpose of assessing the state of the macroorganism.
Laboratory diagnostic methods complement, confirm or exclude the clinical diagnosis. In the practice of a dermatologist, mycological examination (microscopy and culture) is widely used. Microbiological, histological (if benign and malignant neoplasms of the nail bed are suspected) examinations are also carried out. The choice of diagnostic methods depends on the clinical manifestations in the area of the affected nail (nails). Assessment of the nail condition includes an assessment of its shape, surface, thickness, color. An undoubted role in diagnostics is played by the analysis of clinical manifestations in the area of the nail fold.
The diagnosis is determined by the appearance of the changes, microscopic analysis and examination of scrapings are also necessary. Taking the necessary sample is sometimes difficult, since not all affected areas contain fungi. When diagnosing, it is necessary to distinguish between psoriasis and lichen planus.
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Differential diagnosis of onychomycosis
Similar clinical manifestations occur in nails affected by psoriasis, keratoderma, lichen planus and onychodystrophies.
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Treatment of onychomycosis
Treatment of onychomycosis is a very urgent problem in modern dermatology and dermatocosmetology. Quite often this disease becomes a cosmetic problem for patients, significantly affecting the quality of life, psychological and somatic status. Onychomycosis therapy can be external and systemic. The use of external antifungal drugs is justified only in the case of initial damage to the distal part of the nail plate, when no more than a third of it is involved in the process and there is no pronounced subungual hyperkeratosis. In other cases, the use of systemic antifungal drugs is indicated. In general, when choosing a therapy method, the doctor is offered to focus on a set of signs: the volume of involvement of the nail plate (up to 1/3 or more than 1/3), localization of the lesion (distal or proximal), the presence of onychomycosis on the hands and / or feet, the number of affected nails, which fingers are affected, the degree of severity of subungual hyperkeratosis.
The introduction of oral antifungal agents from the azole group (itraconazole, fluconazole) and terbinafine in the mid-1980s, which have a stronger, more selective effect on the enzyme systems of fungi than ketoconazole, was an important achievement in the treatment of superficial and systemic mycoses. The advantages of these agents are a wide spectrum of action, the ability to selectively accumulate and linger in the nail plate without getting back into the bloodstream. Itraconazole (Orungal, etc.), the undoubted advantage of which is the wide spectrum of action (it has a fungicidal effect on filamentous, yeast and mold fungi), is prescribed using the pulse therapy method: 200 mg twice a day during the first week of each month. The duration of treatment for onychomycosis of the hands is 2 months, for onychomycosis of the toes, the drug is recommended to be prescribed for a period of 3 months. The use of pulse therapy for onychomycosis is effective, sharply reduces the incidence of side effects and reduces the total dose of the drug.
Terbinafine (Lamisil, Ekaifin, etc.) is also one of the drugs of choice for the treatment of onychomycosis, especially if it is caused by Dermatophytes. The drug is taken once a day at 250 mg. For onychomycosis of the hands and feet, Lamisil is prescribed for a period of 6 weeks to 3 months.
Fluconazole (Diflucan, Mikosist, etc.) is prescribed for onychomycosis of the hands and feet caused by dermatophytes or mixed microflora. The dosage of the drug is 150 mg once a week for 6 months for onychomycosis of the hands and 6-12 months for onychomycosis of the feet.
It should be emphasized that surgical removal of nails in the treatment of onychomycosis is extremely undesirable due to the possibility of irreversible damage to the matrix and the subsequent development of persistent onychomadesis with the formation of pterygium. The use of modern antimycotics, which have the property of accumulating in the horny appendages of the skin, allows for a long time to maintain a fungicidal concentration in the affected area. Against the background of systemic therapy, external antifungal therapy can be carried out; special forms intended for the nail plate are used - forms of varnish with various antifungal agents (amorolfine - Lotseril, ciclopiroxolamine - Batrafen). In parallel, it is necessary to treat concomitant mycosis of the feet using external antifungal agents. The following groups of drugs are prescribed in the form of cream, ointment, spray:
- ashes: clotrimazole (Clotrimazole, Canesten, Candid, etc.), ketoconazole (Yaizoral), miconazole (Daktarin), bifonazole - (Mikospor), econazole (Pevaryl, etc.), isoconazole (Trtogen);
- allylamines (terbinafine - Lamisil, naftifine - Exoderil);
- morpholine derivatives (amorolfine - Loceryl);
- hydroxypyridone derivatives (cyclopiroxolamine - Batrafen)
- other means.
The total duration of external treatment depends on the individual growth rate of the nail plates. It is recommended to take care of the nail plates, file them regularly, and various keratolytic agents (lactic-salicylic collodion, etc.) can be used.
Treatment of onychomycosis should include not only effective etiologic but also pathogenetic therapy, as well as detection and correction of the underlying concomitant pathology. In parallel with the prescription of antifungal antibiotics, therapy aimed at improving microcirculation in the distal extremities is necessary. Pentoxifylline (Trental, Agapurin) is used at 400 mg 2-3 times a day, calcium supplements (Doxychem, Doxium) at 250-500 mg 3 times a day, nicotinic acid preparations (xanthinol nicotinate 150-300 mg 3 times a day during meals or 1 ml of 1% nicotinic acid solution intramuscularly N 10-15 per course). Patients are shown physiotherapy procedures aimed at improving blood circulation in the distal extremities. For this purpose, various procedures on paravertebral areas in the lumbosacral and cervicothoracic spine can be recommended - UHF therapy, amplipulse therapy, diathermy (N 7-10 daily), etc. Supravascular laser irradiation of blood in the projection of peripheral arteries is also used. The output radiation power is from 15 to 50 mW, the exposure time is 6-10 minutes for each irradiation zone. The areas of exposure, duration and number of procedures are determined by the type of vascular pathology and the type of onychomycosis. To increase the effectiveness of this technique, a device is used to create negative pressure (0.1-0.13 atm) in the laser radiation exposure zone.
The effectiveness of onychomycosis therapy depends largely on the thoroughness of antifungal treatment of shoes and other household items. For this purpose, a 10% formalin solution, a 0.5% chlorhexidine bigluconate solution, and miconazole spray (Daktarin) can be used.
After completion of therapy for onychomycosis, preventive treatment of the nail plates and feet is recommended using modern antifungal creams, varnishes and sprays (groups of drugs: azoles, terbinafine, amorolfine, ciclopiroxolamine, etc.).
To prevent relapse, it is necessary to cut your nails short, dry your feet thoroughly after bathing, and use antifungal powders.