Fontana-positive grains in mycetoma caused by Microsporum canis

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.

Mycetoma caused by Microascus gracilis: a novel agent of human eumycetoma in Sudan

Species of the genus Microascus are uncommon agents of human diseases despite their ubiquitous presence in the environment. In this communication, the first case of white grain eumycetoma caused by the fungus Microascus gracilis is reported. The patient was initially misdiagnosed as having actinomycetoma based on the grains morphological and cytological features and was treated with antimicrobial therapy with no clinical improvement. She underwent wide local surgical excision to improve the response to medical treatment and further grain cultural, molecular and taxonomy techniques were conducted and the diagnosis of mycetoma due to M. gracilis was established. The antifungal susceptibilities of this isolate to nine drugs were tested in vitro and they showed poor activity. Combination therapy with surgery and itraconazole led to complete recovery. A medical literature search revealed no previous report on M. gracilis as a causative agent of eumycetoma and hence we are reporting this new causative agent of human eumycetoma. Also, the difficulty in the management of this patient emphasizes the need for accurate and appropriate diagnostic tests for the identification of mycetoma-causative organisms and thus proper management.

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.

Fontana-Masson stain in fungal infections

BACKGROUND

Fontana-Masson (FM) staining is a histopathology technique used to identify dematiaceous fungi. The result often guides initial species identification and antifungal treatment; however, there is evidence that nondematiaceous fungi might react with this stain. Few studies in the current literature address this issue.

OBJECTIVE

Our aim was to classify the FM staining patterns of common fungal pathogens for use by pathologists attempting to accurately identify fungi on histopathologic examination.

METHODS

In total, 132 cases of culture proven mycoses were identified. We stained tissue with 2 different FM protocols and recorded the intensity and distribution of results.

RESULTS

There was variability in staining, and many nondematiaceous fungi showed positivity, including Zygomycetes, Aspergillus, and Fusarium spp.

LIMITATIONS

The study was limited by the number of cases. Of 132 cases identified, 112 cases had adequate tissue left after sectioning deeper into the block.

CONCLUSION

Nondematiaceous fungi frequently stained positive with FM. The course of treatment should not be based on the result of this stain alone. Histopathology should be examined in multiple tissue sections, and therapy should be determined on the basis of clinical context and culture results.

Disseminated dermatophytic pseudomycetoma caused by Microsporum species

BACKGROUND

Dermatophyte infection is almost exclusively a superficial cutaneous mycosis usually confined to the stratum corneum of nails and hairs of normal hosts. Deep cutaneous and subcutaneous infections due to dermatophytes are exceedingly rare and usually limited to immunosuppressed individuals. These infections remain chronic and persist in spite of treatment.

MATERIALS AND METHODS

We report two clinical cases of disseminated dermatophytic pseudomycetoma caused by Microsporum gypseum and Microsporum canis in immunosuppressed patients.

RESULTS

Patient 1, in 2008, showed improvement with fluconazole, cephalothin, and terbinafine treatment for Microsporum gypseum. After suspension of the treatment, new lesions appeared and culture from material was positive. In 2009, she presented confluent papules and nodules forming plaques on her face and neck with the isolation of Microsporum canis. Clinical response to this treatment was poor. Patient 2 was affected by both tinea corporis due to Trichophyton rubrum and dermatophytic pseudomycetoma caused by Microsporum canis. The response to treatment was successful with oral itraconazole and local surgical excision.

CONCLUSIONS

It is important to recognize these atypical presentations of dermatophytic infections in immunosuppressed patients, which may warrant a more aggressive treatment in order to achieve resolution.

The changing face of Microsporum spp infections

Significant changes in epidemiology, etiology, and the clinical pattern of mycotic infections caused by Microsporum spp have been observed in recent years. Fungal infections caused by M canis, followed by M gypseum and M hominis, involving skin and its appendages, represent one of the most common diseases worldwide and a recalcitrant problem in dermatology that demands appropriate diagnostic and treatment strategies. The most striking clinical phenomena of superficial and kerion and other forms of tinea, such as tinea capitis, fungal infections of the glabrous skin (tinea pedis, manus, cruris et corporis), and even onychomycosis due to Microsporum spp are described, with emphasis on the changes that have occurred in the last decade. The data on significant differences in the prevalence and clinical pattern of the fungal skin infections caused by Microsporum spp today compared with the data at the beginning of the epidemic breakout might still be rather controversial, depending also on the patients' lifestyle and geography. In general, physicians should be aware of the clinical spectrum of mycotic infections due to Microsporum spp to avoid mistakes in identifying the fungal etiology and to provide patients with the proper therapy.

Management of mycetoma: major challenge in tropical mycoses with limited international recognition

PURPOSE OF REVIEW

The present review highlights an orphan infectious disease in alarming need of international recognition. While money is being invested to develop new broad-spectrum antimicrobial drugs to treat infection in general, improvement in the management of complicated infections such as mycetoma receives little support.

RECENT FINDINGS

Many case presentations describe single-center experience in the management of mycetoma. Unfortunately, randomized and blinded clinical studies into the efficacy of antimicrobial treatment are desperately lacking. Response to medical treatment is usually better in actinomycetoma than eumycetoma. Eumycetoma is difficult to treat using current therapies. Surgery in combination with azole treatment is the recommended regimen for small eumycetoma lesions in the extremities. Bone involvement complicates clinical management, leaving surgical amputation as the only treatment option. Although clinical management has not received major attention recently, laboratory technology has improved in areas of molecular diagnosis and epidemiology.

SUMMARY

Management of mycetoma and laboratory diagnosis of its etiological agents need to be improved and better implemented in endemic regions. Optimized therapeutic approaches and more detailed epidemiological data are urgently needed. It is vital to initiate multicenter collaborations on national and international levels to develop consensus clinical score sheets and state-of-the-art treatment regimens for mycetoma patients.