Mycetoma of the scalp due to Microsporum canis: hystopathologic, mycologic, and immunogenetic features in a 6-year-old girl

An updated list of eumycetoma causative agents and their differences in grain formation and treatment response

SUMMARYIn 2023, the World Health Organization designated eumycetoma causative agents as high-priority pathogens on its list of fungal priority pathogens. Despite this recognition, a comprehensive understanding of these causative agents is lacking, and potential variations in clinical manifestations or therapeutic responses remain unclear. In this review, 12,379 eumycetoma cases were reviewed. In total, 69 different fungal species were identified as causative agents. However, some were only identified once, and there was no supporting evidence that they were indeed present in the grain. Madurella mycetomatis was by far the most commonly reported fungal causative agent. In most studies, identification of the fungus at the species level was based on culture or histology, which was prone to misidentifications. The newly used molecular identification tools identified new causative agents. Clinically, no differences were reported in the appearance of the lesion, but variations in mycetoma grain formation and antifungal susceptibility were observed. Although attempts were made to explore the differences in clinical outcomes based on antifungal susceptibility, the lack of large clinical trials and the inclusion of surgery as standard treatment posed challenges in drawing definitive conclusions. Limited case series suggested that eumycetoma cases caused by Fusarium species were less responsive to treatment than those caused by Madurella mycetomatis. However, further research is imperative for a comprehensive understanding.

Histopathology in the Diagnosis of Tinea Capitis: When to Do, How to Interpret?

The diagnosis of tinea capitis is usually made by clinical signs and direct microscopic examination. Early diagnosis of this dermatophytic infection, which may cause permanent hair loss if not treated appropriately, is very crucial. In recent years, the use of dermoscopy has helped with early diagnosis. However, when tinea capitis has an atypical course and develops in adulthood, it can be confused with several diseases, such as psoriasis, seborrheic dermatitis, folliculitis decalvans, acne keloidalis, and dissecting cellulitis. Due to the different treatment approaches and prognoses, it is important to distinguish tinea capitis from invasive dermatoses on the scalp. In this article, histopathological findings of tinea capitis and several advantages and disadvantages of histopathology in the diagnosis of fungal infections are also reviewed and updated.

Fatal dermatophytic pseudomycetoma in a patient with non-HIV CD4 lymphocytopenia

Dermatophytic pseudomycetoma is a rare invasive infection, involving both immunocompetent and immunocompromised individuals. Since the discovery of inherited immune disorders such as the impairment of CARD9 gene, extended dermatophyte infections are mostly ascribed to any of these host factors. This study is to present and explore the potential causes in a fatal dermatophytic pseudomycetoma patient. We present a chronic and deep pseudomycetoma caused by the common dermatophyte Microsporum canis which ultimately led to the death of the patient. Mycological examination, genetic studies and host immune responses against fungi were performed to explore the potential factors. The patient had decreased lymphocyte counts with significantly reduced CD4⁺ T cells, although all currently known genetic parameters proved to be normal. Through functional studies, we demonstrated that peripheral blood mononuclear cells from the patient showed severe impairment of adaptive cytokine production upon fungus-specific stimulation, whereas innate immune responses were partially defective. This is, to our knowledge, the first report of fatal dermatophytic pseudomycetoma in a patient with non-HIV CD4 lymphocytopenia, which highlights the importance of screening for immune deficiencies in patients with deep dermatophytosis.

Skin Immunity to Dermatophytes: From Experimental Infection Models to Human Disease

Dermatophytoses (ringworms) are among the most frequent skin infections and are a highly prevalent cause of human disease worldwide. Despite the incidence of these superficial mycoses in healthy people and the compelling evidence on chronic and deep infections in immunocompromised individuals, the mechanisms controlling dermatophyte invasion in the skin are scarcely known. In the last years, the association between certain primary immunodeficiencies and the susceptibility to severe dermatophytosis as well as the evidence provided by novel experimental models mimicking human disease have significantly contributed to deciphering the basic immunological mechanisms against dermatophytes. In this review, we outline the current knowledge on fungal virulence factors involved in the pathogenesis of dermatophytoses and recent evidence from human infections and experimental models that shed light on the cells and molecules involved in the antifungal cutaneous immune response. The latest highlights emphasize the contribution of C-type lectin receptors signaling and the cellular immune response mediated by IL-17 and IFN-γ in the anti-dermatophytic defense and skin inflammation control.

Mycetoma caused by Microsporum canis in a patient with renal transplant: A case report and review of the literature

Microsporum canis is a dermatophyte known to cause superficial skin infections. In immunocompromised patients, it can lead to invasive dermatophytosis. We present a case of biopsy-proven left knee mycetoma caused by M canis in a renal transplant patient. Identification of M canis was achieved via sequencing of the internal transcribed spacer regions. Treatment involved surgical debridement, oral posaconazole, and reduction in immunosuppression. In addition, we provide a review of current literature on invasive M canis infections.

Changing Concepts and Current Definition of Majocchi's Granuloma

Dermatophytic granuloma characterized by perifollicular granulomatous inflammation was first described by Domenico Majocchi and was later named after him, Majocchi's granuloma (MG). Although the initial description was related to a dermatophyte Trichophyton tonsurans, later reports linked MG to non-dermatophytes (Phoma, Aspergillus, Malbranchea), which led to a confusion of disease patterns caused by cutaneous pathogens and general opportunistic microorganisms. Furthermore, several causative agents of MG described in the literature were not confirmed as such. Our review addressed the following aspects: (1) significance of histopathological finding for MG diagnosis, (2) dermatophytes as exclusive agents of MG, (3) spectrum of etiological agents causing different types of invasive dermatophytic infections, and (4) treatment options.

IL-17-Mediated Immunity Controls Skin Infection and T Helper 1 Response during Experimental Microsporum canis Dermatophytosis

Despite worldwide prevalence of superficial mycoses, the immune response in dermatophytosis has scarcely been investigated. In this study, we developed a model of superficial skin infection in C57BL/6 mice with Microsporum canis, a highly prevalent human pathogen. This model mimics mild inflammatory human dermatophytosis, characterized by neutrophil recruitment and fungal invasion limited to the epidermis and exhibits the establishment of a specific T helper type 17 immune response during infection. By using IL-17RA- or IL-17A/F-deficient mice we showed that, in the absence of a functional IL-17 pathway, M. canis extensively colonizes the epidermis and promotes an exaggerated skin inflammation and a shift to an IFN-γ-mediated (T helper type 1) response. IL-17 signaling was not involved in neutrophil influx to skin or fungal invasion to deeper tissues. Finally, this study shows that skin langerin-expressing cells contribute to the antifungal T helper type 17 response in vivo. In conclusion, these data directly show a dual function of IL-17 cytokines in dermatophytosis by controlling superficial infection and down-modulating a T helper type 1 antifungal response.

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.

Global burden of human mycetoma: a systematic review and meta-analysis

Mycetoma is a chronic infectious disease of the subcutaneous tissue with a high morbidity. This disease has been reported from countries between 30°N and 15°S since 1840 but the exact burden of disease is not known. It is currently unknown what the incidence, prevalence and the number of reported cases per year per country is. In order to estimate what the global burden of mycetoma is, a meta-analysis was performed. In total 50 studies were included, which resulted in a total of 8763 mycetoma cases. Most cases were found in men between 11 and 40 years of age. The foot was most commonly affected. Most cases were reported from Mexico, Sudan and India. Madurella mycetomatis was the most prevalent causative agent world-wide, followed by Actinomadura madurae, Streptomyces somaliensis, Actinomadura pelletieri, Nocardia brasiliensis and Nocardia asteroides. Although this study represents a first indication of the global burden on mycetoma, the actual burden is probably much higher. In this study only cases reported to literature could be used and most of these cases were found by searching archives from a single hospital in a single city of that country. By erecting (inter)national surveillance programs a more accurate estimation of the global burden on mycetoma can be obtained.