Researchers collected skin, hair and nail specimens from patients attending private mycology clinics and governmental university hospitals in Ardabil, Fars, Golestan, Isfahan, Khuzestan, Mazandaran, Razavi Khorasan, Tehran and West Azerbaijan. Every included patient had fungal elements visible by direct KOH microscopy in at least one sample, and culture recovered dermatophytes from 1,568 of the 2,211 suspected cases, a yield of 70.9%.

The researchers combined a lineage-specific PCR with ITS rDNA sequencing, restriction analysis and haplotype comparisons. The specific PCR identified 1,191 isolates as T. mentagrophytes var. indotineae. Sequencing of 78 randomly selected PCR-positive isolates confirmed their placement within the lineage: 57 represented two sub-genotypes of ITS genotype VIII, while 20 belonged to a previously unrecognised genotype XXIX within the T. mentagrophytes var. indotineae lineage. The study used the variety designation in line with taxonomic databases and recent population-genetic studies.

Clinical forms involving the groin and trunk predominated. Tinea cruris accounted for 656 cultured infections, or 41.8% of the total, followed by tinea corporis with 376 cases, or 23.9%; mixed tinea cruris and tinea corporis accounted for 144 cases, or 9.2%, and generalised infection accounted for 128, or 8.2%. T. mentagrophytes var. indotineae was identified in 544 of 656 tinea cruris cases, 279 of 376 tinea corporis cases, 110 of 144 mixed cruris and corporis cases, and 112 of 128 generalised infections. It was also found in 17 of 29 nail infections and 17 of 45 cases of tinea capitis.

Patients with T. mentagrophytes var. indotineae infection had a mean age of 34.5 ± 13.6 years, a median of 35 and a range of 1–85. The group included 588 males and 603 females, with no statistically significant difference in sex distribution (p = 0.664). Species distribution was associated with age group, province, clinical form and involved body site, with all reported p-values below 0.001. The largest numbers of confirmed infections came from Khuzestan, with 607 cases, followed by Mazandaran with 130 and Ardabil and Fars with 115 each.

Among 73 confirmed cases with reliable patient histories, none had documented travel abroad. This absence of recorded international travel does not establish where infection was acquired, but it means travel alone cannot explain the lineage’s presence in the surveyed population. Retrospective analysis placed several Iranian isolates collected in 2011 and 2015 within genotype VIII, indicating that the lineage was already present before the earliest reports from the Indian subcontinent. The study also identified genotype XXIX, adding to previously reported local genetic diversity. Related lineages have been recovered from sheep in rural Iran, but a local animal reservoir remains an unconfirmed hypothesis, and the data do not resolve the lineage’s geographic origin or centre of diversity.

Partial sequencing of the squalene epoxidase gene, SQLE, in 410 T. mentagrophytes var. indotineae isolates detected mutations in 184 isolates, or 44.8%. The mutations comprised the F397L amino-acid substitution in 132 mutant isolates, representing 71.7%, and L393S in 52, representing 28.3%. Mutation proportions were highest in Khuzestan at 52.4% and Fars at 46%, and lowest in Golestan at 8.5%. Both substitutions have previously been associated with terbinafine resistance in isolates from Asia and Europe. The reported 44.8% frequency was higher than mutation rates of 17.8% in an Iranian survey from 2020 and 14.35% in one from 2024, although the present study sequenced only part of the SQLE gene and targeted mutations at positions 393 and 397, so other mutations may not have been detected.

No antifungal susceptibility testing was performed, and the study did not collect clinical outcome data demonstrating treatment failure. The findings therefore identify a substantial proportion of isolates carrying mutations associated with likely terbinafine resistance, but they do not directly establish phenotypic resistance or explain individual treatment outcomes. The hospital-based design and reliance on patients referred to specialised clinics also limit how directly the observed proportions can be applied to Iran’s general population.

Overall, the survey documents a major shift in the epidemiology of referred dermatophytosis in Iran: T. mentagrophytes var. indotineae was the leading identified cause across the sampled settings and was detected in skin, scalp and nail infections. The authors said the findings highlight the need for routine molecular identification, SQLE genotyping and stronger national surveillance, while broader genomic studies and integration of clinical outcome data are needed to clarify transmission, origin and therapeutic implications.

Subject of Research: Epidemiology and terbinafine-resistance-associated SQLE mutations in Iranian dermatophyte isolates

Article Title: Dermatophytosis in Iran: a sharp increase in cases caused by Trichophyton mentagrophytes var. indotineae

Article References: Takesh, A., Wennrich, A., Kolařík, M., Zarei-Mahmoudabadi, A., Kiasat, N., Pazyar, N., Rafiei, A., Abastabar, M., Haghani, I., Kharazi, M., Basiri, S., Jahanshiri, Z., Khodadadi, H., Mohammadi, R., Zarrinfar, H., Seifi, Z., Diba, K., Kamali Sarvestani, H., & Rezaei-Matehkolaei, A. (2026). Dermatophytosis in Iran: a sharp increase in cases caused by Trichophyton mentagrophytes var. indotineae. IMA Fungus, 17, Article e180817. https://doi.org/10.3897/imafungus.17.180817

Image Credits: AI Generated

DOI: 10.3897/imafungus.17.180817

Keywords: dermatophytosis, Trichophyton mentagrophytes, T. mentagrophytes var. indotineae, Iran, terbinafine resistance, SQLE mutations, tinea cruris, tinea corporis, molecular surveillance, fungal infection, sharp, increase

Dermatophytosis, the family of superficial fungal infections that includes ringworm, jock itch, and athlete’s foot, is one of the most common infectious conditions on Earth, affecting roughly a quarter of the world’s population according to the World Health Organization. For decades, the allylamine drug terbinafine served as the reliable first-line oral treatment. That changed dramatically in India beginning around 2016, when dermatologists began reporting an unprecedented wave of chronic, widespread, and recurrent tinea infections that failed to respond to standard therapy. The culprit strains, initially described as Trichophyton mentagrophytes internal transcribed spacer genotype VIII, showed minimum inhibitory concentrations to terbinafine far above the wild-type range and produced atypical clinical pictures with large, steroid-modified lesions. Genetic analyses, including multilocus sequence typing and ITS sequencing, eventually confirmed that these isolates formed a distinct species, which Kano and colleagues named Trichophyton indotineae in 2020.

The taxonomy itself carries practical weight. Until recently, the T. mentagrophytes and T. interdigitale species were tangled in a morphological knot, with zoophilic and anthropophilic variants blurring species boundaries. Multicentric Indian studies, genomic analyses by Pchelin, Singh, and Tang and their teams, and whole-genome comparisons ultimately established T. indotineae as a genetically separate lineage that behaves as a human-adapted pathogen. Because phenotypic appearance alone cannot reliably separate it from close relatives, molecular taxonomy has become essential not just for academic clarity but for surveillance, since understanding which species is spreading and where determines how resistance trends are tracked and interpreted.

The epidemiology revealed by the review is striking. In India, prevalence figures for the organism vary widely, from 6.8 percent to as high as 61.5 percent in northern regions and 6.09 to 27.6 percent in the south, suggesting that climatic conditions are not the dominant driver. Between 2017 and 2019, T. indotineae became the predominant dermatophyte across India, accounting for roughly 82.6 to 94 percent of isolates in multicentre studies, displacing the long-standing leader Trichophyton rubrum. GenBank sequences suggest the organism circulated in the region for more than a decade before the epidemic was formally recognized. Patients now account for an estimated 5 to 10 percent of new dermatology outpatient registrations in northern India, and researchers describe hospital figures as merely the tip of the iceberg in the community.

Beyond the Indian subcontinent, the fungus has established a troubling international footprint. Iran appears to be a second endemic region, with earliest documented cases dating back to 2008 to 2010; a multicentre Iranian study found 28 of 141 T. mentagrophytes complex isolates were T. indotineae, some with terbinafine MICs of 32 milligrams per liter or higher. In a 2019 Baghdad survey, 69.2 percent of complex isolates were identified as T. indotineae, with 39 percent showing terbinafine resistance. Imported and locally acquired cases have been confirmed in Belgium, Canada, Denmark, France, Germany, Greece, Japan, and Switzerland, while Poland has deposited ITS sequences with 100 percent identity to the species. Retrospective sequencing pushed the earliest European detection back to 2011 in Germany. Most diagnosed patients were migrants from South Asian countries, but a Canadian study reporting an average delay of more than a year between migration and lesion onset raises the possibility of local transmission, and refugee or migrant camps with overcrowding may serve as transmission hotspots in non-endemic regions.

Clinically, the infection is dominated by extensive tinea corporis and tinea cruris, often covering large areas of the lower body and groin, with tinea faciei frequently reported. Notably, both men and women are affected equally regardless of age, and the fungus primarily infects people with competent immunity. Diabetes and immunosuppression appear to play only a minor role; instead, the local skin environment and drug pressure determine disease course. Intrafamilial transmission is a hallmark, with roughly half of patients reporting spread within the household, often linked to shared clothing, towels, and other fomites. Tinea capitis has not been established as a recognized manifestation, though the review cautions that earlier scalp infections may have been misassigned without molecular identification.

The molecular basis of terbinafine resistance is now well characterized. Terbinafine works by binding and blocking squalene epoxidase, the fungal enzyme encoded by the SQLE gene that is required to synthesize ergosterol, an essential component of the fungal cell membrane. In resistant strains, point mutations alter the enzyme’s structure so the drug can no longer bind effectively. The dominant substitutions are Leu393Phe and Phe397Leu, with additional mutations including L393S, F397I, F397V, F415I, F415S, F415V, H440Y, S395P, Q408L, and S443P documented. A multicentre Indian study found up to 76 percent of T. indotineae isolates resistant in vitro, and even T. rubrum showed resistance in 57.1 percent of tested isolates, signaling that allylamine resistance extends beyond a single species. Aggregate MIC data show in vitro terbinafine resistance in 78.9 to 82.5 percent of isolates, with MICs of 4 micrograms per milliliter or higher in 70.5 percent of isolates tested by CLSI methods. Resistance to azoles is also emerging, driven by overexpression of efflux pump genes; genomic work on T. rubrum identified 39 ATP-binding cassette transporters and 170 major facilitator superfamily transporters, of which several, including TruMDR1, TruMDR2, TruMDR3, and TruMFS2, are overexpressed on azole exposure and actively expel drugs from fungal cells.

Diagnosis and treatment remain the weakest links. Conventional phenotypic methods cannot reliably distinguish T. indotineae from its relatives, so ITS sequencing is the reference approach, albeit slow and dependent on sequencing facilities and curated databases. Faster alternatives include species-specific PCR targeting the C120-287 locus, PCR-RFLP targeting TOP2, and quantitative PCR assays that detect species-specific ITS polymorphisms directly from clinical specimens, though these still require validation. Improved MALDI-TOF mass spectrometry databases have proven remarkably powerful: adding reference spectra raised identification from 5 percent to 96 percent with 99.6 percent sensitivity. On the therapeutic side, itraconazole remains the most effective systemic alternative, with in vitro resistance relatively rare, while newer topical azoles such as luliconazole, sertaconazole, and efinaconazole show strong efficacy for localized disease. Expert recommendations favor itraconazole 100 milligrams per day as a first-line option and individualized, prolonged therapy continued until complete clinical and mycological cure, guided wherever possible by susceptibility testing.

The review’s authors close with a blunt prescription. Over-the-counter fixed-dose combinations containing potent corticosteroids such as clobetasol with antifungals and antibiotics are a major engine of the epidemic, with 60 to 70 percent of tinea patients reporting prior exposure; steroids deliver temporary relief while suppressing local immunity and distorting lesion appearance. Fungal resistance data is rarely integrated into national surveillance systems, and regulatory oversight of combination creams is inadequate, especially in developing countries. The authors call for a WHO-coordinated dermatophyte surveillance framework, standardized laboratories with molecular diagnostics, antifungal stewardship programs that match drug, dose, and duration to susceptibility results, prescription-only restrictions on steroid-antifungal combinations, and high-quality multicentre randomized controlled trials, which are currently absent, to establish evidence-based regimens for what has become the first truly global epidemic of drug-resistant ringworm.

Subject of Research: Global emergence of terbinafine-resistant dermatophytosis caused by Trichophyton indotineae

Article Title: The global emergence of Trichophyton indotineae: epidemiology, resistance, and management challenges

Article References: Shaw, D., Omar, A., Singh, M., Chandanathil, M., Bhargavi, C., Mysore, N., Bir, D., Ramasamy, S., & Honnavar, P. (2026). The global emergence of Trichophyton indotineae: epidemiology, resistance, and management challenges. Frontiers in Tropical Diseases, 7, Article 1960706. https://doi.org/10.3389/fitd.2026.1960706

Image Credits: AI Generated

DOI: 10.3389/fitd.2026.1960706

Keywords: Trichophyton indotineae, dermatophytosis, terbinafine resistance, antifungal resistance, squalene epoxidase, tinea, itraconazole, efflux pumps, molecular diagnostics, antifungal stewardship, global health, India epidemic

The fungus at the center of the study is Trichophyton rubrum, the dermatophyte most commonly responsible for ringworm and other superficial skin, hair, and nail infections in humans. Dermatophytes are among the most prevalent fungal pathogens worldwide, yet surprisingly little is known about whether they harbor mycoviruses and whether those viruses influence their behavior. To address this gap, the research team first screened clinical isolates of Trichophyton species for the presence of mycoviruses. They then turned to an experimental strategy that has rarely been applied to dermatophytes: heterologous transfection, the deliberate introduction of a virus from one host species into an entirely different one.

The virus chosen for the experiment was Terfezia claveryi endornavirus 1, abbreviated TcEV1, originally described in the desert truffle Terfezia claveryi. Endornaviruses form a distinctive group among mycoviruses. They possess double-stranded RNA genomes, lack the capacity to produce conventional virus particles, and are typically transmitted vertically through cell division and spores rather than spreading horizontally between individuals. Because of these properties, endornavirus infections are often described as cryptic, meaning they persist permanently within host lineages without producing virions or obvious symptoms. This cryptic lifestyle has made it difficult to assess what, if anything, endornaviruses do to their hosts, and has left open the question of whether they can jump between fungal species in nature or in the laboratory.

By introducing TcEV1 into T. rubrum through heterologous transfection, the researchers created a unique experimental system: a human pathogenic fungus carrying a viral passenger from a distant fungal lineage. The comparison between virus-free and virus-infected isolates of the same fungus allowed the team to isolate the specific effects of the virus from the background of the fungus’s own genetics. This controlled design is critical in mycovirus research, where differences between fungal strains can easily be mistaken for viral effects if the comparison is not carefully constructed.

The phenotypic consequences of TcEV1 infection were striking. Under laboratory conditions at 30 degrees Celsius, a temperature favorable to dermatophyte growth, the virus-infected isolate displayed increased radial growth compared with its virus-free counterpart. Radial growth rate is a standard measure of fungal fitness in vitro, reflecting how quickly a colony can expand across a substrate. The infected isolate also showed a significant rise in conidiation capacity, meaning it produced more conidia, the asexual spores through which dermatophytes spread from host to host and from lesion to lesion. Enhanced spore production could plausibly translate into greater transmissibility in a clinical setting, since the infectious dose of dermatophytes depends on the number of viable conidia shed by an infected individual.

The most consequential result, however, emerged from the in vivo experiments. Using a murine skin infection model, the researchers compared the ability of virus-free and TcEV1-infected T. rubrum to colonize living skin tissue. The virus-infected isolate achieved a fungal load approximately 2.5 times higher than the virus-free isolate. This roughly two-and-a-half-fold increase in fungal burden indicates that the presence of the endornavirus substantially enhanced the fungus’s capacity to establish and maintain infection in host tissue. The authors describe this as the first evidence of mycovirus-mediated enhanced virulence in T. rubrum, a finding that reframes mycoviruses from biological curiosities into potential modifiers of human disease severity.

Compounding the picture of heightened pathogenic potential, TcEV1 infection was also associated with reduced susceptibility to two major classes of antifungal agents: the echinocandins and amphotericin B. Echinocandins inhibit the synthesis of beta-glucan, a key structural component of the fungal cell wall, and are a mainstay of systemic antifungal therapy, while amphotericin B binds ergosterol in the fungal membrane and remains one of the most broadly active antifungal drugs available. A shift toward reduced susceptibility in a virus-carrying isolate suggests that mycoviral infection could complicate the treatment of dermatophytosis, although the study’s observations were made in vitro and the clinical implications for patients would require further investigation.

The mechanistic basis for these changes remains an open question. Endornaviruses encode RNA helicase motifs and other replication-associated proteins, and their persistent double-stranded RNA replicative form is a well-known trigger of antiviral responses in many host systems. In fungi, chronic viral infection can reshape metabolism, stress responses, and gene regulation in ways that alter growth and virulence. In plant-associated fungi, mycoviruses have been documented to attenuate virulence, as in the famous case of chestnut blight hypovirulence, but examples of mycoviruses increasing the pathogenicity of a human fungal pathogen are exceedingly rare. The T. rubrum system therefore offers a valuable platform for dissecting how a persistent RNA virus reprograms a dermatophyte’s physiology, from cell wall architecture to spore development and interaction with host tissue.

The study also carries broader implications for how mycologists and clinicians think about fungal disease. If cross-species transmission of mycoviruses can convert a cryptic infection into a driver of enhanced virulence and drug tolerance, then the viral status of clinically important fungi becomes a variable worth monitoring. Screening for mycoviruses could one day complement conventional susceptibility testing, particularly for isolates that behave unusually in the clinic. The finding that an endornavirus from a truffle-associated fungus can establish itself in a dermatophyte also hints that the boundaries between mycoviral host ranges may be more permeable than previously assumed, raising the possibility that such transfers occur in natural settings where fungi share environments.

The research originated from the master’s thesis of Aysenur Simsek at Dokuz Eylul University’s Institute of Science and was supported by the Scientific and Technological Research Council of Türkiye under project number 122Z630 and by Dokuz Eylul University under project number FYL-2025-3680. The corresponding authors are Tetiana Krupodorova of the National Academy of Sciences of Ukraine in Kyiv and Ergin Sahin of Dokuz Eylul University. As the first demonstration that heterologous transfection of an endornavirus can enhance the virulence of a major human dermatophyte both in culture and in a living host, the work opens a new chapter in the study of fungal viruses, one in which the invisible RNA passengers of fungi may help determine how aggressively those fungi infect us and how well our drugs work against them.

Subject of Research: Mycovirus-mediated enhancement of virulence and antifungal resistance in the dermatophyte Trichophyton rubrum

Article Title: Heterologous transfection of an endornavirus alters the phenotype of Trichophyton rubrum in vitro and in vivo

Article References: Simsek, A., Ozturk, N., Akata, I., Batir, M. B., Kaya, S., Kaya, E., Krupodorova, T., Sevindik, M., Edis, G., & Sahin, E. (2026). Heterologous transfection of an endornavirus alters the phenotype of Trichophyton rubrum in vitro and in vivo. Virology Journal. https://doi.org/10.1186/s12985-026-03295-y

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03295-y

Keywords: mycovirus, endornavirus, Trichophyton rubrum, dermatophytosis, TcEV1, heterologous transfection, virulence, antifungal resistance, echinocandins, amphotericin B, murine infection model, double-stranded RNA

The dog was referred to the Veterinary Clinic of the Faculty of Veterinary Medicine at the University of Tehran with a striking dermatological picture. It lived outdoors under unsanitary conditions with regular exposure to vegetation and soil, and it presented with diffuse hair loss, marked redness, itching and scaling across the skin of its back. Crucially, there was no ulceration or open wound, no lethargy and no loss of appetite, so systemic illness seemed unlikely and a complete blood count was not performed. The owner declined a skin biopsy, which meant the team could not obtain histopathological evidence of fungal invasion, a detail that would later shape how carefully the conclusions had to be framed. Hair plucks and skin scrapings were collected from the affected areas under sterile conditions and sent to the laboratory for fungal examination.

The initial diagnostic workup followed the standard playbook for suspected dermatophytosis, the superficial fungal infection of keratinized skin that is usually caused by organisms such as Microsporum canis, Microsporum gypseum or Trichophyton mentagrophytes. A Wood’s lamp examination was negative, and a direct microscopic examination of material treated with 10 percent potassium hydroxide also failed to reveal fungal elements. But the story changed when the samples were cultured on Sabouraud Dextrose Agar. After incubation at 28 degrees Celsius, colonies emerged that were creamy-brown and powdery with a colorless reverse surface. Lactophenol cotton blue staining of the growth revealed thin, septate hyphae studded with large, round, warty conidia, a morphological signature that immediately suggested the team was not dealing with a routine dermatophyte.

Seeking to probe the organism’s thermal behavior, the researchers subcultured the colonies onto blood agar and incubated them at 37 degrees Celsius, close to mammalian body temperature, for five days. The fungus produced creamy, dome-shaped, mucoid colonies under these conditions, and Giemsa staining revealed round-to-oval yeast-like cells with budding and point attachments when viewed under oil immersion at 100 times magnification. This dimorphic tendency, the ability to alter its appearance under different growth conditions, added another layer of complexity to the identification. Morphology alone could not settle the question, particularly since members of the family Chaetomiaceae, to which Corynascus belongs, are notorious for overlapping phenotypic features among closely related species. The team therefore turned to the laboratory’s molecular arsenal.

Genomic DNA was extracted from the isolate using a commercial fungal DNA extraction kit, and the internal transcribed spacer region of ribosomal DNA, comprising the ITS1 spacer, the 5.8S rRNA gene and the ITS2 spacer, was amplified with the universal primers ITS1 and ITS4. The polymerase chain reaction protocol began with denaturation at 94 degrees Celsius for three minutes, followed by 37 cycles of denaturation for 30 seconds, annealing at 60 degrees Celsius for 30 seconds and extension at 72 degrees Celsius for 30 seconds, with a final extension of eight minutes. The roughly 600-base-pair amplicon was then sequenced, and the resulting sequence was deposited in GenBank under accession number PV082530, making it publicly available for future comparisons by researchers anywhere in the world.

The sequence told a clear story. BLAST analysis showed 99.36 percent nucleotide similarity to reference sequences of Corynascus verrucosus and 99.34 percent similarity to a reference sequence of Corynascus sepedonium, a closely related species whose ITS region differs only marginally. To resolve the placement further, the researchers aligned their sequence with reference data from GenBank and constructed a maximum likelihood phylogenetic tree in MEGA7 using the Kimura two-parameter model with 1000 bootstrap replicates. The Iranian isolate fell squarely within the broader Corynascus lineage and clustered tightly with C. verrucosus sequences from different geographic regions, while reference sequences annotated as Myceliophthora, including Myceliophthora sepedonium and Myceliophthora verrucosa, occupied the same larger assemblage. The tree was rooted with Amesia atrobrunnea as the outgroup, and the resulting topology was consistent with previously published taxonomic frameworks placing Corynascus within the family Chaetomiaceae.

The taxonomy behind that placement is itself a story of scientific revision. The genus Corynascus comprises seven recognized species, and its boundaries have shifted repeatedly over decades of study, from early work by von Klopotek in 1974 and Stchigel and colleagues in 2000, who described three new thermotolerant species, to a 2015 re-evaluation of Myceliophthora using morphological and multilocus phylogenetic data that affirmed Corynascus as a distinct genus. More recent comprehensive studies have supported that distinction using multigene analyses incorporating ITS, LSU, rpb2, tub2 and tef sequences. Meanwhile, members of the Myceliophthora lineage have attracted industrial attention for their production of thermostable enzymes, and C. verrucosus itself made headlines in 2020 when researchers documented it as a mycoendophyte of Croton bonplandianus and a potential source of bioactive metabolites active against multidrug-resistant pathogens and cancer cells. None of this industrial or pharmacological relevance implies pathogenicity, a distinction the authors are careful to draw.

Where might a pet dog have encountered such a fungus? Environmental studies of composting offer a suggestive clue. Research on organic waste and manure composting has documented substantial shifts in fungal community composition as physicochemical conditions change, with thermophilic and thermotolerant fungi, exactly the ecological guild to which many Corynascus species belong, flourishing in these habitats. Composting environments and similar organic-material settings may therefore serve as reservoirs of environmentally adapted fungal taxa. The Tehran patient’s outdoor lifestyle, unsanitary surroundings and regular contact with soil and vegetation provided ample opportunity for exposure. Still, the authors emphasize that phylogenetic relatedness does not imply shared biological function or pathogenic potential, and that genetic similarity alone should never be read as evidence of a shared disease-causing role.

The clinical narrative, however, lends weight to a genuine association rather than a chance contaminant. The same fungal species was recovered on three independent cultures from the lesion, no bacterial growth was detected, and mite infestation was excluded. The dog was treated with oral ketoconazole combined with ketoconazole shampoo, receiving four weekly medicated baths. The itching and redness resolved within about a month, hair regrowth followed, and a uniform coat had returned approximately six months after treatment began. Over a nine-month follow-up period, the original cutaneous signs never recurred. The combination of repeated isolation, exclusion of other pathogens, molecular identification and clinical improvement following antifungal therapy supports, though it does not prove, a causal link.

That caution about proof is the intellectual heart of the report. Because histopathological examination was never performed, tissue invasion by the fungus could not be demonstrated directly, and the authors explicitly frame the finding as an association rather than definitive evidence of causality. Their broader message concerns method: for uncommon environmental fungi recovered from veterinary specimens, accurate identification demands a polyphasic approach that integrates morphology, ITS sequencing and phylogenetic placement rather than relying on any single line of evidence. Molecular methods can rescue isolates that fail to produce characteristic reproductive structures in culture, but they carry their own biases and limited discriminatory power, as the near-identical ITS sequences of C. verrucosus and C. sepedonium illustrate. By expanding the documented occurrence of C. verrucosus to a canine cutaneous lesion, the case adds a small but genuinely novel data point to veterinary mycology and a reminder that the fungal world’s opportunists may be more numerous, and better camouflaged, than current diagnostics routinely reveal.

Subject of Research: A rare case of cutaneous infection by the environmental fungus Corynascus verrucosus in a Shih Tzu dog, identified through molecular and phylogenetic analysis.

Article Title: A Rare Case of Cutaneous Infection by Corynascus verrucosus in a Shih Tzu Dog: Molecular Identification and Phylogenetic Analysis

Article References: Ghahremani, M., Sharifzadeh, A., Ashrafi Tamai, I., & Faridfar, G. (2026). A Rare Case of Cutaneous Infection by Corynascus verrucosus in a Shih Tzu Dog: Molecular Identification and Phylogenetic Analysis. Veterinary Medicine and Science, 12(5), Article e71205. https://doi.org/10.1002/vms3.71205

Image Credits: AI Generated

DOI: 10.1002/vms3.71205

Keywords: Corynascus verrucosus, veterinary mycology, canine dermatology, fungal infection, ITS sequencing, phylogenetic analysis, Chaetomiaceae, dermatophytosis, Shih Tzu, molecular identification, environmental fungi, ketoconazole treatment