Tinea imbricata: autosomal dominant pattern of susceptibility in a polygamous indigenous family of the Nahuatl zone in Mexico. Tinea imbricata: Autosomal dominierendes Anfalligkeitsmuster in einer poligamen Eingeborenen-Familie in Nahuatl, Mexiko

Review on host-pathogen interaction in dermatophyte infections

Dermatophytosis is a common superficial fungal infection of the skin and its appendages caused by dermatophytes. Recent times have witnessed a dynamic evolution of dermatophytes driven by their ecology, reproduction, pathogenicity and host immune response, influenced by population migration and socioeconomic status. Dermatophytes establish infection following successful adherence of arthroconidia to the surface of keratinized tissues. The proteolytic enzymes released during adherence and invasion not only ascertain their survival but also allow the persistence of infection in the host. While the cutaneous immune surveillance mechanism, after antigen exposure and presentation, leads to activation of T lymphocytes and subsequent clonal expansion generating effector T cells that differentially polarize to a predominant Th17 response, the response fails to eliminate the pathogen despite the presence of high levels of IFN-γ. In chronic dermatophytosis, antigens are a constant source of stimulus promoting a dysregulated Th17 response causing inflammation. The host-derived iTreg response fails to counterbalance the inflammation and instead polarizes to Th17 lineage, aggravating the chronicity of the infection. Increasing antifungal resistance and recalcitrant dermatophytosis has impeded the overall clinical remission. Human genetic research has the potential to generate knowledge to explore new therapeutic targets. The review focuses on understanding specific virulence factors involved in pathogenesis and defining the role of dysregulated host immune response against chronic dermatophytic infections for future management strategies.

Annular infectious dermatoses

Annular configuration is conspicuous in the clinical manifestation of many skin diseases and can be helpful for the diagnosis and differential diagnosis. Variations may include arciform, ring-form, annular, circinate, serpiginous, gyrated, polycyclic, targeted or figurate forms, in different colors, sizes, and numbers, with various textures and surfaces. In infectious dermatoses, the annular reactions can be specific or nonspecific, while the underlying mechanisms remain largely unknown. In the specific reactions caused by direct invasion of the pathogens, the contest between the centrifugal outspread of the infectious agents and the centripetal impedance of the host immune response is supposed to determine the final conformation. Examples include erythema infectiosum, orf, erythema multiforme, and pityriasis rosea of viral origin. Bacterial infections that may display annular lesions include erythrasma, erythema (chronicum) migrans of Lyme borreliosis, secondary syphilis, cutaneous tuberculosis, and leprosy. Superficial mycosis, such as dermatophytosis, candida intertrigo, tinea imbricata, and subcutaneous mycosis, such as chromoblastomycosis, and algae infection protothecosis, are characterized by annular progression of the skin lesions. The creeping serpiginous extension is an alarming sign for the diagnosis of cutaneous larva migrans. A better understanding of the virulence and pathogenicity of the pathogens and the way and type of immune response will help to clarify the pathogenesis.

Tinea Imbricata among the Indigenous Communities: Current Global Epidemiology and Research Gaps Associated with Host Genetics and Skin Microbiota

Tinea imbricata is a unique fungal skin disease that mostly affects indigenous populations in Southeast Asia, Oceania, and Central and South America. The control and management of this disease among these communities are challenging given their remote locations, certain traditional practices, and severe malnutrition status. To date, there are only a handful of reports published globally, which highlights the need for a more holistic approach in addressing this skin disease. Several bodies of evidence and reports have shown that host genetic factors have a profound influence on the pathogenesis of tinea imbricata, while skin microbiota is touted to have a role in the pathogenesis of the disease. However, there are limited studies of how host genetics and skin microbiota impact disease susceptibility in the host. To improve the understanding of this disease and to find possible long-term effective treatment among the affected indigenous communities, a comprehensive literature review is needed. Hence, this review paper aims to present the current status of tinea imbricata among the indigenous communities, together with published findings on the possible underlying reasons for its specific distribution among these communities, particularly on the ways in which host skin microbiota and host genetics affect occurrence and disease patterns. This information provides valuable insights for future research by highlighting the current knowledge gaps in these areas.

Genetic Predisposition and its Heredity in the Context of Increased Prevalence of Dermatophytoses

Dermatophytosis is a widespread disease with high prevalence and a substantial economic burden associated with costs of treatment. The pattern of this infectious disease covers a wide spectrum from exposed individuals without symptoms to those with acutely inflammatory or non-inflammatory, chronic to invasive, and life-threatening symptoms. Moreover, the prevalence of cutaneous fungal infections is not as high as might be expected. This curious disparity in the dermatophyte infection patterns may suggest that there are individual factors that predispose to infection, with genetics as an increasingly well-known determinant. In this review, we describe recent findings about the genetic predisposition to dermatophyte infections, with focus on inheritance in families with a high frequency of dermatophyte infections and specific host-pathogen interactions. The results of studies indicating a hereditary predisposition to dermatophytoses have been challenged by many skeptics suggesting that the varied degree of pathogenicity and the ecological diversity of this group of fungi are more important in increasing sensitivity. Nonetheless, a retrospective analysis of the hereditary propensity to dermatophytoses revealed at least several proven genetic relationships such as races, CARD9 deficiency, HLA-DR4 and HLA-DR8 type and responsible genes encoding interleukin-22, β-defensin 2 and 4 as well as genetic defects in dectin-1, which increased the prevalence of the disease in families and were involved in the inheritance of the proneness in their members. In future, the Human Genome Diversity Project can contribute to elucidation of the genetic predisposition to dermatophytoses and provide more information.

Superficial mycoses, a matter of concern: Global and Indian scenario-an updated analysis

Superficial mycoses of skin, nails and hair are among the common fungal infections. They are caused by dermatophytes, non-dermatophyte moulds, yeasts and yeast-like fungi. Such fungal infections are widespread all over the world and are predominant in tropical as well as subtropical regions. Environmental factors, such as warm, humid and pitiable hygienic conditions, are conducive for their growth and proliferation. Although it does not cause mortality, it is known to be associated with excessive morbidity which may be psychological or physical. This affects the quality of life of the infected individuals which leads to a negative impact on their occupational, emotional and social status. Such infections are increasing on a global scale and, therefore, are of serious concern worldwide. This review article covers the global and Indian scenario of superficial mycoses taking into account the historical background, aetiological agents, prevalence, cultural and environmental factors, risk factors, pathogenesis and hygienic practices for the prevention of superficial mycoses.

Senna (Cassia) alata (Linn.) Roxb. leaf decoction as a treatment for tinea imbricata in an indigenous tribe in Southern Philippines

BACKGROUND

Tinea imbricata, a rare form of tinea corporis caused by Trichophyton concentricum, is endemic to the T'boli tribe in the Southern Philippines. Temporary remissions and limited access to antifungal medications make its treatment a pressing public health concern. Anecdotal reports about the use of Senna alata leaf decoction as treatment exist.

OBJECTIVE

To determine the efficacy of community-prepared S alata leaf decoction in the treatment of tinea imbricata.

METHODS

Tinea imbricata patients were instructed to apply S alata leaf decoction for 4 weeks (28 ± 3 days). Disease severity, pruritus visual analogue scale scores (VAS) and potassium hydroxide (KOH) mounts of skin scrapings were evaluated before and after treatment. Two assessors evaluated disease severity based on photographs. Cohen's kappa statistics were used to assess diagnostic concordance. Adverse drug events were recorded.

RESULTS

Twenty patients were enrolled. After 4 weeks, 95% had decreased pruritus VAS scores, with a mean decreased of 4.05 after treatment (P < .0001). There was a significant difference in disease severity scores before and after treatment (P ≤ .05) with an overall agreement of 'moderate' for both assessors (κ = 0.6, 95% CI [0.33, 0.87]). Forty per cent had negative KOH tests after treatment. None had adverse drug events.

CONCLUSION

This is the first study that showed the potential of a community-prepared leaf decoction as a treatment option for tinea imbricata. Larger clinical trials establishing its efficacy, effectiveness and safety profile are recommended to enable its promotion among the indigenous people and health authorities as an accessible and affordable treatment for tinea imbricata.

Advances in Understanding Human Genetic Variations That Influence Innate Immunity to Fungi

Fungi are ubiquitous. Yet, despite our frequent exposure to commensal fungi of the normal mammalian microbiota and environmental fungi, serious, systemic fungal infections are rare in the general population. Few, if any, fungi are obligate pathogens that rely on infection of mammalian hosts to complete their lifecycle; however, many fungal species are able to cause disease under select conditions. The distinction between fungal saprophyte, commensal, and pathogen is artificial and heavily determined by the ability of an individual host's immune system to limit infection. Dramatic examples of commensal fungi acting as opportunistic pathogens are seen in hosts that are immune compromised due to congenital or acquired immune deficiency. Genetic variants that lead to immunological susceptibility to fungi have long been sought and recognized. Decreased myeloperoxidase activity in neutrophils was first reported as a mechanism for susceptibility to Candida infection in 1969. The ability to detect genetic variants and mutations that lead to rare or subtle susceptibilities has improved with techniques such as single nucleotide polymorphism (SNP) microarrays, whole exome sequencing (WES), and whole genome sequencing (WGS). Still, these approaches have been limited by logistical considerations and cost, and they have been applied primarily to Mendelian impairments in anti-fungal responses. For example, loss-of-function mutations in CARD9 were discovered by studying an extended family with a history of fungal infection. While discovery of such mutations furthers the understanding of human antifungal immunity, major Mendelian susceptibility loci are unlikely to explain genetic disparities in the rate or severity of fungal infection on the population level. Recent work using unbiased techniques has revealed, for example, polygenic mechanisms contributing to candidiasis. Understanding the genetic underpinnings of susceptibility to fungal infections will be a powerful tool in the age of personalized medicine. Future application of this knowledge may enable targeted health interventions for susceptible individuals, and guide clinical decision making based on a patient's individual susceptibility profile.

In vitro models of dermatophyte infection to investigate epidermal barrier alterations

Fungal infections of the skin, known as dermatophytoses, are initiated at the epidermal barrier and lead to dysfunctions of the stratum corneum and cornified skin appendages. Dermatophytosis affects a significant part of the human population and, despite the availability of effective treatments, its prevalence is still increasing. Numerous dermatophyte species are able to induce lesions in both animals and humans, with different clinical pictures and host inflammatory responses. The understanding of the infectious process and of tissue responses has been impeded by discrepancies between observations in vivo or in research models. Indeed, cells cultured as monolayers do not undergo the keratinization process required to study the adherence and invasion of dermatophytes. Animal models lack relevance to study human dermatophytosis because of species-specific differences in the development of lesions and inflammatory responses. This review focuses on the recent development of cultured human skin equivalents, which partly overcomes those limitations and allows improved understanding of the pathogenesis of dermatophytosis in human being, especially the impacts of infection on epidermal barrier integrity.

Host- and pathogen-dependent susceptibility and predisposition to dermatophytosis

Dermatophytes are a highly specialized group of keratinophilic and keratinolytic filamentous fungi causing a ringworm disease called dermatophytosis or superficial mycoses. Although dermatophyte infections do not threaten the host's life, they lower its quality in humans by causing discomfort related to cosmetic problems and through their epidemiological significance, whereas in farm animals they are responsible for economic losses and constitute a source of the spread of spores. Evidence from countless observational studies that have been conducted over the last 90 years indicates that dermatophytes infect humans of every age, race, gender and socioeconomic status with strikingly high rates, as well as both farmed and wild animals in various health conditions and with various epidemiological statuses. However, the prevalence of superficial fungal infections is highly variable, since it depends on several parameters associated with the infected individual and the dermatophyte, their mutual interactions, and epidemiological and geographical factors. The curious disparity in dermatophyte infection patterns has prompted many investigators to search for a link between the host, the host's predispositions and susceptibility to the disease, and the dermatophyte species and virulence. Thus, the question arises as to whether, in addition to the generally recognized factors predisposing hosts to diseases, there are some other predispositions to dermatophyte infections in a species-specific host. In this review, we describe recent findings about the mechanism of dermatophyte infections, focusing on the adaptation of the fungi to the host and conditions predisposing each side to the disease.

Tinea Imbricata: An Overview

BACKGROUND

Tinea imbricata is a chronic superficial mycosis caused mainly by Trichophyton concentricum. The condition mainly affects individuals living in primitive and isolated environment in developing countries and is rarely seen in developed countries. Physicians in nonendemic areas might not be aware of this fungal infection.

OBJECTIVE

To familiarize physicians with the clinical manifestations, diagnosis, and treatment of tinea imbricata.

METHODS

A PubMed search was completed in Clinical Queries using the key terms "Tinea imbricata" and "Trichophyton concentricum". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, reviews, and case reports. The information retrieved from the above search was used in the compilation of the present article.

RESULTS

The typical initial lesions of tinea imbricata consist of multiple, brownish red, scaly, pruritic papules. The papules then spread centrifugally to form annular and/or concentric rings that can extend to form serpinginous or polycyclic plaques with or without erythema. With time, multiple overlapping lesions develop, and the plaques become lamellar with abundant thick scales adhering to the interior of the lesion, giving rise to the appearance of overlapping roof tiles, lace, or fish scales. Lamellar detachment of the scales is common. The diagnosis is mainly clinical, based on the characteristic skin lesions. If necessary, the diagnosis can be confirmed by potassium hydroxide wet-mount examination of skin scrapings of the active border of the lesion which typically shows short septate hyphae, numerous chlamydoconidia, and no arthroconidia. Currently, oral terbinafine is the drug of choice for the treatment of tinea imbricata. Combined therapy of an oral antifungal agent with a topical antifungal and keratolytic agent may increase the cure rate.

CONCLUSION

In most cases, a spot diagnosis of tinea imbricata can be made based on the characteristic skin lesions consisting of scaly, concentric annular rings and overlapping plaques that are pruritic. Due to popularity of international travel, physicians involved in patient care should be aware of this fungal infection previously restricted to limited geographical areas.

Genetic Predictors of Susceptibility to Dermatophytoses

Countless observational studies conducted over the last century reveal that dermatophytes infect humans of every age, race, gender, and socioeconomic status with strikingly high rates. The curious disparity in dermatophyte infection patterns observed within and between populations has led countless investigators to explore whether genetics underlie a susceptibility to, or confer protection against, dermatophyte infections. This paper examines the data that offer a link between genetics and dermatophytoses and discusses the underlying mechanisms that support these observations.

Tropical Skin Diseases in Children: A Review- Part I

Because of travel and migration patterns, tropical skin diseases are now seen all around the world, not just in tropical or developing countries. Nutrition, housing, and environmental factors play an important role in these infectious diseases, so when they appear out of their normal environments, their classic presentation may vary. Tropical diseases can also present differently in childhood, making their recognition, diagnosis, and management a clinical challenge. Health care providers in developed countries need to be familiar with tropical skin diseases and be able to diagnose them in returning travelers or immigrants in order to optimize care. This article aims to review the epidemiologic, clinical, diagnostic, and therapeutic aspects of some of the most common tropical dermatologic conditions in children.

Tinea Imbricata in an Italian Child and Review of the Literature

Tinea imbricata is a chronic superficial mycosis caused by Trichophyton concentricum. It is characterized by widespread, annular, concentric, squamous lesions. Tinea imbricata is endemic in three geographical areas: Southwest Pacific, Southeast Asia, and Central and South America. Tinea imbricata in travelers returning from endemic areas is exceptionally rare. We report a case of tinea imbricata in an Italian child who acquired the infection during a trip to Solomon Islands. Three cultures were positive for T. concentricum. The patient was successfully treated with griseofulvin and terbinafine cream.

New insights into genes, immunity, and the occurrence of dermatophytosis

Fungal infections in humans are among the most prevalent diseases globally. Superficial invasion by dermatophytes leads to skin, hair, and nail infection. Even though they have usually been associated with extrinsic conditions such as immunosuppression, environmental factors, and contaminated individuals, objects, or surfaces; people are not equally susceptible to dermatophyte infection, even when they have the same risk factors. This commentary summarizes findings that provide evidence of familial or genetic predisposition to fungal infection, mediated by innate and/or adaptive immunity.

Trichophyton Tonsurans Infection Manifesting as Multiple Concentric Annular Erythemas

We report a case of dermatophytosis in a Judo wrestler caused by Trichophyton tonsurans (T. tonsurans) with clinical features that mimicked the concentric rings of tinea imbricata. Tinea imbricata is a unique dermatophytosis caused by Trichophyton concentricum (T. concentricum), observed endemically in subtropical to torrid zones and characterized by impressive concentric rings. We found three similar cases of the dermatophytosis in the literature that were reported as tinea pseudoimbricata or tinea indecisiva. All of these cases were associated with systemic or local immunosuppression, perhaps simulating the mechanism of tinea imbricata, which is known to involve the lack of delayed type hypersensitivity to T. concentricum. These cases imply that iatrogenic immunosuppression may perhaps play an important role in the development of the unique clinical features mimicking tinea imbricata. Furthermore, three of the four cases, including the presented case, were caused by T. tonsurans. It may be necessary to consider T. tonsurans infection when multiple concentric erythemas are encountered.

Tinea imbricata in the Americas

PURPOSE OF REVIEW

The aim is to provide an overview on tinea imbricata, or Tokelau, a superficial mycosis caused by Trichophyton concentricum, a strictly anthropophilic dermatophyte with a well-defined geographic distribution and predisposing factors that include genetic, racial and immunologic susceptibility patterns and a specific environment.

RECENT FINDINGS

This review covers the most interesting aspects of the infrequent disease tinea imbricata, including the historical background, the epidemiologic aspects, highlighting the genetic and racial patterns of susceptibility to the acquisition of the disease, and the immunologic aspects that help to explain its clinical behavior. We also present a clinical description of the disease, the differential diagnosis and how currently some other emerging diseases such as syphilis in immunocompromised patients can mimic tinea imbricata. The therapeutic options are still griseofulvin and nowadays terbinafine, but the access to the treatments in the endemic zones and the changes in habits of the affected population make control and prevention of the disease difficult.

SUMMARY

Tinea imbricata, or Tokelau, remains an infrequent superficial mycosis restricted to endemic zones in the South Pacific islands (Polynesia and Melanesia), South Asia and some specific areas of South America. Migration phenomena and global changes in the climate may modify the incidence and characteristics of the disease.