Genetic predisposition - understanding underlying mechanisms of onychomycosis

Updated Perspectives on the Diagnosis and Management of Onychomycosis

Onychomycosis is the most common nail disease encountered in clinical practice and can cause pain, difficulty with ambulation, and psycho-social problems. A thorough history and physical examination, including dermoscopy, should be performed for each patient presenting with nail findings suggestive of onychomycosis. Several approaches are available for definitive diagnostic testing, including potassium hydroxide and microscopy, fungal culture, histopathology, polymerase chain reaction, or a combination of techniques. Confirmatory testing should be performed for each patient prior to initiating any antifungal therapies. There are several different therapeutic options available, including oral and topical medications as well as device-based treatments. Oral antifungals are generally recommended for moderate to severe onychomycosis and have higher cure rates, while topical antifungals are recommended for mild to moderate disease and have more favorable safety profiles. Oral terbinafine, itraconazole, and griseofulvin and topical ciclopirox 8% nail lacquer, efinaconazole 10% solution, and tavaborole 5% solution are approved by the Food and Drug Administration for treatment of onychomycosis in the United States and amorolfine 5% nail lacquer is approved in Europe. Laser treatment is approved in the United States for temporary increases in clear nail, but clinical results are suboptimal. Oral fluconazole is not approved in the United States for onychomycosis treatment, but is frequently used off-label with good efficacy. Several novel oral, topical, and over-the-counter therapies are currently under investigation. Physicians should consider the disease severity, infecting pathogen, medication safety, efficacy and cost, and patient age, comorbidities, medication history, and likelihood of compliance when determining management plans. Onychomycosis is a chronic disease with high recurrence rates and patients should be counseled on an appropriate plan to minimize recurrence risk following effective antifungal therapy.

Transmission of Onychomycosis and Dermatophytosis between Household Members: A Scoping Review

Onychomycosis is a common fungal infection of the nail, caused by dermatophytes, non-dermatophytes, and yeasts. Predisposing factors include older age, trauma, diabetes, immunosuppression, and previous history of nail psoriasis or tinea pedis. Though many biological risk factors have been well characterized, the role of the environment has been less clear. Studies have found evidence of transmission in 44% to 47% of households with at least one affected individual, but the underlying mechanisms and risk factors for transmission of onychomycosis between household members are incompletely understood. A scoping literature review was performed to characterize and summarize environmental risk factors involved in the transmission of onychomycosis within households. A total of 90 papers met the inclusion criteria, and extracted data was analyzed in an iterative manner. Shared household surfaces may harbor dermatophytes and provide sources for infection. Shared household equipment, including footwear, bedding, and nail tools, may transmit dermatophytes. The persistence of dermatophytes on household cleaning supplies, linen, and pets may serve as lasting sources of infection. Based on these findings, we provide recommendations that aim to interrupt household transmission of onychomycosis. Further investigation of the specific mechanisms behind household spread is needed to break the cycle of transmission, reducing the physical and social impacts of onychomycosis.

A Mycological and Molecular Epidemiologic Study on Onychomycosis and Determination In Vitro Susceptibilities of Isolated Fungal Strains to Conventional and New Antifungals

Background

Onychomycosis is one of the most common and recurrent dermatological diseases worldwide. The antimycotic activity of prescribed medications varies according to the causative agents, and treatment failure rates exceeding 30%. This study aimed to assess the epidemiological profile of onychomycosis in Iran. Also, the susceptibilities to conventional and new antifungals were investigated.

Methods

In this descriptive cross-sectional study, during the period of 18 months starting from September 2019 until March 2020, 594 nail specimens were obtained from patients who presented nail changes compatible with a clinical diagnosis of onychomycosis. The patients were referred from different cities, including Tehran, Kermanshah, Arak, Kashan, Rasht, Qom, Urmia, Zahedan, Hamadan, Zanjan, Borujerd, Bushehr, and Yazd. All the samples were subjected to microscopic examination and fungal culture. Fungi identified were confirmed through the PCR-sequencing method. The susceptibility to itraconazole, fluconazole, terbinafine, griseofulvin, posaconazole, ravuconazole, efinaconazole, luliconazole, and tavaborole was evaluated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, document M38-A2 for filamentous fungi, and document M27-A3 for yeasts.

Results

594 patients were included. Of these, in 179 cases (30.1%) (95% CI:0.3 ± 0.037) onychomycosis was confirmed. The majority of patients were ≥ 60 years of age (n=58, 32.6%) and female (n=113, 63.1%). Saprophytic fungi accounted for the vast majority of the nail isolates (n=92, 51.4%) (95% CI:0.051 ± 0.0.073), followed by dermatophytes (n=45, 25.1%) (95% CI:0.25 ± 0.063), and yeasts (n=42, 23.5%) (95% CI:0.23 ± 0.061). Diabetes mellitus (77.3%), hypothyroidism (18.2%), and solid tumors (4.5%) were documented as the most prevalent underlying conditions. Antifungal susceptibility testing was performed against 60 fungal isolates (20 each of Candida species, saprophytic fungi, and dermatophytes). Efinaconazole, ravuconazole, and luliconazole were the most active agents against Candida species. Also, luliconazole, posaconazole, and efinaconazole were most potent against dermatophytes. Luliconazole had the greatest antifungal activity against saprophytic fungi.

Conclusions

The prevalence of onychomycosis in Iranian patients was relatively high. LUL exhibited potent antifungal activity against the three groups of fungi tested, determining its broad-spectrum antimycotic activity and its probable use as the first-line therapy for onychomycosis.

Onychomycosis in children - review on treatment and management strategies

BACKGROUND

Onychomycosis is an uncommon condition in children with increasing global prevalence. Health practitioners should confirm the diagnosis through mycology examination and examine family members of affected individuals for onychomycosis and tinea pedis.

OBJECTIVE

To comprehensively summarize the treatment and management strategies for pediatric onychomycosis.

METHODS

We performed a comprehensive literature search in the PubMed database to identify clinical studies on treatment for mycologically-confirmed dermatophyte onychomycosis in children <18 years. The exclusion criteria were combination therapy, case reports, reviews, systematic reviews and duplicate studies.

RESULTS

Per-weight dosing regimens of systemic antifungal agents such as terbinafine, itraconazole, and fluconazole are found to be safe in children and are used off-label for the treatment of pediatric onychomycosis with high efficacy. Topical antifungal agents such as ciclopirox, efinaconazole, and tavaborole have established safety and efficacy in children. Children respond better than adults to topical therapy due to their thinner, faster growing nails. There is no data on the efficacy of medical devices for onychomycosis in children.

CONCLUSION

Efinaconazole topical solution 10% and tavaborole topical solution 5% are FDA approved for the treatment of onychomycosis in children ≥6 years; ciclopirox topical solution 8% nail lacquer is approved in children ≥12 years.

The efficacy and safety of pulse vs. continuous therapy for dermatophyte toenail onychomycosis

BACKGROUND

Onychomycosis is a chronic, fungal infection of the nails. Complete cure remains challenging, but oral antifungal medications have been successful in managing the fungus for a significant proportion of patients. Treatment with these drugs can be continuous or intermittent, albeit the evidence on their relative efficacies remains unclear.

OBJECTIVE

To determine the relative effectiveness and safety of pulse versus continuous administration, of three common oral therapies for dermatophyte onychomycosis, by conducting multiple-treatment meta-analysis.

METHODS

This systematic review and network meta-analysis compared the efficacy (as per mycological cure) and adverse event rates of three oral antifungal medications in the treatment of dermatophyte toenail onychomycosis, namely terbinafine, itraconazole and fluconazole. A total of 30 studies were included in the systematic review, while 22 were included in the network meta-analysis.

RESULTS

The likelihood of mycological cure was not significantly different between continuous and pulse regimens for each of terbinafine and itraconazole. Use of continuous terbinafine for 24 weeks - but not 12 weeks - was significantly more likely to result in mycological cure than continuous itraconazole for 12 weeks or weekly fluconazole for 9-12 months. Rank probabilities demonstrated that 24-week continuous treatment of terbinafine was the most effective. There were no significant differences in the likelihood of adverse events between any continuous and pulse regimens of terbinafine, itraconazole and fluconazole. Drug treatments were similar to placebo in terms of their likelihood of producing adverse events.

CONCLUSION

More knowledge about the fungal life cycle and drugs' pharmacokinetics in nail and plasma could further explain the relative efficacy and safety of the pulse and continuous treatment regimens. Our results indicate that in the treatment of dermatophyte toenail onychomycosis, the continuous and pulse regimens for terbinafine and itraconazole have similar efficacies and rates of adverse events.

Emerging drugs for the treatment of onychomycosis

Introduction: Onychomycosis is a widespread nail disease, often occurring on the feet. It is a chronic and often recurring disease, which makes it difficult to eradicate. The infection may be caused by dermatophytes, non-dermatophyte molds, and yeasts. Traditionally, systemic antifungal medications have been used to treat this infection, but in recent years topical formulations have been the focus of research.Areas covered: This review outlines the current antifungal market and novel treatments currently in development or in experimental phases. It highlights a shift from systemic treatments to topical options as well as penetration enhancers. There are also several novel systemic options in development.Expert opinion: Although there have been significant developments in treatment options for onychomycosis, it remains a challenging chronic condition with less than desirable cure rates. This may be attributed to the formation of fungal biofilms and limited understanding of the fungal lifecycle. However, when patients adhere to treatment protocols and employ preventative measures, outcomes are generally favorable.

Recent advances in therapies for onychomycosis and its management

Onychomycosis is the most common affliction of the nail. It may be caused by dermatophytes, yeasts, and non-dermatophyte molds. Traditionally, oral antifungal treatments have been used to treat the fungus, although they can be accompanied by side effects and drug interactions. Topical treatments provide an alternative modality, bypassing the systemic effects of oral drugs; recent research has centered on topical drug improvement and development. Physical and laser treatments are being used in conjunction with topicals, which may help penetrate the thick nail plate. In this review, techniques from all categories are outlined: both novel experimental approaches and progress and effectiveness of recently developed treatments. More long-term studies are required to determine the efficacy of various treatments, but cure rates are improved when patients adhere to treatments and follow preventative measures to avoid disease recurrence.

[Prevalence of dermatomycoses in professional football players : A study based on data of German Bundesliga fitness check-ups (2013-2015) compared to data of the general population]

BACKGROUND

The prevention, early diagnosis and treatment of onychomycosis is of great importance for professional athletes to avoid physical limitations by complications. So far, there is only little data on the prevalence of dermatomycosis in professional athletes.

OBJECTIVES

The aim of the study was to detect the prevalence of dermatomycosis in professional football players compared to the general population.

MATERIALS AND METHODS

The prospective, non-interventional, controlled study on the prevalence of dermatomycosis in professional football players was carried out on football players of a German Bundesliga team compared with a previously studied, equivalently aged German working population. A questionnaire survey, a dermatological check-up and a microbiological detection of pathogens in cases of suspicion were performed.

RESULTS

Data of 84 football players (n = 45 in 2013; n = 39 in 2015) were compared to data of n = 8186 male employees between 17 and 35 years of age. In the group of athletes, there were findings of 60.7% onychomycosis, 36.9% of tinea pedis and 17.8% of pityriasis versicolor. In the group of the age-equivalent general German working population the findings were: onychomycosis 3.3%, tinea pedis 3.2%, pityriasis versicolor 1.4%.

CONCLUSION

Our study shows a clearly higher risk for fungal diseases of the skin especially on the feet of professional football players. The results show a necessity for elucidation within prevention and the establishment of an appropriate therapy of dermatomycosis for professional football players.

The Diagnosis and Treatment of Nail Disorders

BACKGROUND

Nail disorders can arise at any age. About half of all nail disorders are of infectious origin, 15% are due to inflammatory or metabolic conditions, and 5% are due to malignancies and pigment disturbances. The differential diagnosis of nail disorders is often an area of uncertainty.

METHODS

This review is based on publications and guidelines retrieved by a selective search in PubMed, including Cochrane reviews, meta-analyses, and AWMF guidelines.

RESULTS

Nail disorders are a common reason for derma - tologic consultation. They are assessed by clinical inspection, dermatoscopy, diagnostic imaging, microbiological (including mycological) testing, and histopathological examination. Some 10% of the overall population suffers from onychomycosis, with a point prevalence of around 15%. Bacterial infections of the nails are rarer than fungal colonization. High-risk groups for nail disorders include diabetics, dialysis patients, transplant recipients, and cancer patients. Malignant tumors of the nails are often not correctly diagnosed at first. For subungual melanoma, the mean time from the initial symptom to the correct diagnosis is approximately 2 years; this delay is partly responsible for the low 10-year survival rate of only 43%.

CONCLUSION

Evaluation of the nail organ is an important diagnostic instrument. Aside from onychomycosis, which is a common nail disorder, important differential diagnoses such as malignant diseases, drug side effects, and bacterial infections must be considered.

Low DEFB4 copy number and high systemic hBD-2 and IL-22 levels are associated with dermatophytosis

Dermatophytes initiate dermatophytosis, but susceptibility to infection is dictated by host genetic factors, although the role of some of these-such as human beta-defensin 2 (hBD-2) genomic (DEFB4) copy number (CN) variation and its induction by IL-22-remains unclear. This was investigated in this cross-sectional study in 442 unrelated Caucasian subjects, including 195 healthy controls and 247 dermatophytosis patients who were divided into five subgroups according to clinical presentation. DNA samples were evaluated for DEFB4 CN variation by relative quantification using the comparative CT method, and serum hBD-2 and IL-22 levels were determined by ELISA. DEFB4 CN in patients was significantly lower and, except in the tinea cruris subgroup, serum hBD-2 levels were higher than in controls. The positive correlation between hBD-2 levels and DEFB4 CN observed in controls was not detected in patients, who also had higher serum IL-22 levels that were positively correlated with hBD-2 levels. Moreover, unlike in control subjects, the serum IL-22 level was negatively correlated with DEFB4 CN in patients. Taken together, these findings suggest an association between decreased DEFB4 CN, elevated serum hBD-2 and IL-22 levels, and dermatophytosis, underscoring a gene/cytokine interaction in the occurrence of this infection.

Morphopathological aspects of healthy nails and nails affected by onychomycosis

Patients of onychomycosis are common in the dermatology practice. Contemporary morphology creates opportunities to study the functional units of the nail when such infections occur from morphopathological point of view. There were 22 nails biopsies from onychomycosis patients taken for the research of morphopathological changes in the thickened nail plate affected by onychomycosis. Samples of cadaverous' nails were used as a control material. The material was stained with haematoxylin and eosin and immunohistochemical methods. Terminal deoxynucleotidyl transferase dUTP nick end labelling reaction and periodic acid-Schiff reaction were also performed. We found patchy hypertrophy in the granulose layer of the epidermis, with focal acanthosis. In the horn layer, we identified nests of parakeratosis of various sizes, with incorporations of homogenous and eosinophil masses. We found high levels of interleukin 6 and interleukin 10 positive cells in the nail bed and in the bloodstream. Interleukin 1, however, was not a part of any of the functional units of any of the nails. Significant amount of fibres containing human beta defensin-2 were found in the bed and plate of the nail. Therefore one can conclude that as regards the nails affected by onychomycosis, the most effective morphopathogenical processes include cytokine and defensin excretion occurrence in the nail bed.

Mycology - an update. Part 1: Dermatomycoses: causative agents, epidemiology and pathogenesis

Dermatomycoses are caused most commonly by dermatophytes. The anthropophilic dermatophyte Trichophyton rubrum is still the most frequent causative agent worldwide. Keratinolytic enzymes, e.g. hydrolases and keratinases, are important virulence factors of T. rubrum. Recently, the cysteine dioxygenase was found as new virulence factor. Predisposing host factors play a similarly important role for the development of dermatophytosis of the skin and nails. Chronic venous insufficiency, diabetes mellitus, disorders of cellular immunity, and genetic predisposition should be considered as risk factors for onychomycosis. A new alarming trend is the increasing number of cases of onychomycosis - mostly due to T. rubrum - in infancy. In Germany, tinea capitis is mostly caused by zoophilic dermatophytes, in particular Microsporum canis. New zoophilic fungi, primarily Trichophyton species of Arthroderma benhamiae, should be taken into differential diagnostic considerations of tinea capitis, tinea faciei, and tinea corporis. Source of infection are small household pets, particularly rodents, like guinea pigs. Anthropophilic dermatophytes may be introduced by families which immigrate from Africa or Asia to Europe. The anthropophilic dermatophytes T. violaceum, T. tonsurans (infections occurring in fighting sports clubs as "tinea gladiatorum capitis et corporis") and M. audouinii are causing outbreaks of small epidemics of tinea corporis and tinea capitis in kindergartens and schools. Superficial infections of the skin and mucous membranes due to yeasts are caused by Candida species. Also common are infections due to the lipophilic yeast fungus Malassezia. Today, within the genus Malassezia more than 10 different species are known. Malassezia globosa seems to play the crucial role in pityriasis versicolor. Molds (also designated non-dermatophyte molds, NDM) are increasingly found as causative agents in onychomycosis. Besides Scopulariopsis brevicaulis, several species of Fusarium and Aspergillus are found.

[Fungal nail infections--an update: Part 1--Prevalence, epidemiology, predisposing conditions, and differential diagnosis]

Onychomycosis describes a chronic fungal infection of the nails most frequently caused by dermatophytes, primarily Trichophyton rubrum. In addition, yeasts (e. g. Candida parapsilosis), more rarely molds (Scopulariopsis brevicaulis), play a role as causative agents of onychomycosis. However, in every case it has to be decided if these yeasts and molds are contaminants, or if they are growing secondarily on pathological altered nails. The point prevalence of onychomycosis in Germany is 12.4%, as demonstrated within the "Foot-Check-Study", which was a part of the European Achilles project. Although, onychomycosis is rarely diagnosed in children and teens, now an increase of fungal nail infections has been observed in childhood. More and more, diabetes mellitus becomes important as significant disposing factor both for tinea pedis and onychomycosis. By implication, the onychomycosis represents an independent and important predictor for development of diabetic foot syndrome and foot ulcer. When considering onychomycosis, a number of infectious and non-infectious nail changes must be excluded. While psoriasis of the nails does not represent a specific risk factor for onychomycosis, yeasts and molds are increasing isolated from patients with psoriatic nail involvement. In most cases this represents secondary growth of fungi on psoriatic nails. Recently, stigmatization and impairment of quality of life due to the onychomycosis has been proven.

An update on treatment of onychomycosis

Onychomycosis (OM) is a fungal infection of the nail plate or nail bed which is highly prevalent in the general population and also responsible for significant morbidity. The condition needs to be treated in view of the physical and emotional handicap it produces. The peculiarities of the nail apparatus in health and disease lead to difficulties in being able to successfully treat this condition. Hence, the very same antifungals which produce high cure rates in skin infections are rendered less efficacious in nail disease. Low cure rates and high relapse rates even with highly efficacious antifungals have lead to an increasing interest in exploring newer treatment options which can ensure drug penetration, drug persistence, mycological cure and effective prevention of relapse. The current review aims to summarize our current status of knowledge about the treatment options for OM. It also summarizes the newer areas of research especially with respect to devices related therapies; physical measures to enhance penetration through nail; and development and evaluation of synergistic combinations.

Pathogenesis of tinea

Dermatophytes are hyphomycetes that can degrade keratin. This puts them in a position to cause infections of the keratin-containing superficial skin. The resulting clinical picture is called tinea. The pathogenesis and course of tinea is decisively determined by pathogen-related factors and by the defense mechanisms of the host. An infection starts with an adherence of fungal propagules, followed by the formation of hyphae that can spread within the tissue. This process is accompanied by a release of fungal enzymes and other pathogenic factors. Next keratinocytes are activated, the epidermal barrier is destroyed, epidermal proliferation is enhanced and defensins are expressed within the epidermis. In addition, innate and specific immune responses are initiated, involving neutrophilic granulocytes, macrophages, antibodies and T cells. The cellular mechanisms are thought to be crucial for healing. Special conditions apply to nail infections, because within nail plates the fungi are not accessible to effective defense mechanisms, as well as to infections of hair follicles that contain specific concentrations of steroid hormones. Dermatophytes that penetrate into the dermis can cause granulomatous inflammatory reactions and systemic immune reactions are supposed to be a trigger of so-called id reactions.

Isolation of transcripts over-expressed in human pathogen Trichophyton rubrum during growth in keratin

Trichophyton rubrum is a cosmopolitan and anthropophilic fungus able to invade keratinized tissue, causing infection in human skin and nails. This work evaluated the changes in the extracellular pH during its growth in keratin (after 6, 12, 24, 48, 72h and 7 days) at initial pH 5.0. We observed a gradual increase of basal pH under keratin exposure when compared to glucose condition. Also, we identified 576T. rubrum transcripts differentially expressed by subtractive suppression hybridization (SSH) using conidia cultivated for 72h in keratin as tester, and cultivated in glucose as driver. The over-expression of 238 transcripts obtained under keratin condition was confirmed by macro-array dot-blot, revealing 28 unigenes. Putative proteins encoded by these genes showed similarity to fungi proteins involved in basic metabolism, growth and virulence, i.e., transporters ABC-MDR, MFS and ATPase of copper, NIMA interactive protein, Gag-Pol polyprotein, virulence factors serine-protease subtilisin and metalloprotease, cytochrome P450, GlcN-6-phosphate deaminase and Hsp30. The upregulation of T. rubrum genes encoding subtilisin, metalloprotease and Gag-Pol polyprotein was also validated by northern blot. The results of this study provide the first insight into genes differentially expressed during T. rubrum grown in keratin that may be involved in fungal pathogenesis.

Strain differentiation of Trichophyton rubrum by randomly amplified polymorphic DNA and analysis of rDNA nontranscribed spacer

Trichophyton rubrum is the most common pathogen causing dermatophytosis. Molecular strain-typing methods have recently been developed to tackle epidemiological questions and the problem of relapse following treatment. A total of 67 strains of T. rubrum were screened for genetic variation by randomly amplified polymorphic DNA (RAPD) analysis, with two primers, 5′-d[GGTGCGGGAA]-3′ and 5′-d[CCCGTCAGCA]-3′, as well as by subrepeat element analysis of the nontranscribed spacer of rDNA, using the repetitive subelements TRS-1 and TRS-2. A total of 12 individual patterns were recognized with the first primer and 11 with the second. Phylogenetic analysis of the RAPD products showed a high degree of similarity (>90 %) among the epidemiologically related clinical isolates, while the other strains possessed 60 % similarity. Specific amplification of TRS-1 produced three strain-characteristic banding patterns (PCR types); simple patterns representing one copy of TRS-1 and two copies of TRS-2 accounted for around 85 % of all isolates. It is concluded that molecular analysis has important implications for epidemiological studies, and RAPD analysis is especially suitable for molecular typing in T. rubrum.

Patients at risk of onychomycosis - risk factor identification and active prevention

OBJECTIVES

The aims of this workshop were to identify risk factors for onychomycosis and to reach consensus on the management of high-risk groups to allow the development of guidelines to help doctors recognize risk factors that complicate treatment.

RESULTS AND CONCLUSIONS

Previous Trichophyton rubrum infection, older age, abnormal nail morphology, immunodeficiency and genetic factors were identified as risk factors for initial infections. Risk factors for recurrence (relapse and re-infection) are largely the same. The experts agreed that the prevention of onychomycosis and its recurrence should be based on the correct treatment of tinea pedis, screening family members and adequate patient education. In addition, generic management recommendations for each high-risk group were discussed: * Immunosuppressed patients Usual dose and treatment length not appropriate Follow-up required Beware of drug interactions * Diabetics Prophylactic foot care combined with nail treatment Good opportunity for patient education, footwear, foot care, etc. Beware of drug interactions * Psoriatics and patients with abnormal nails Dermatophyte eradication does not restore normal nails * Children High failure rate possibly due to compliance problems.