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Tinea corporis and tinea cruris
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Tinea corporis is a dermatophyte infection of the skin of the trunk and extremities, excluding the hair, nails, palms, soles, and the groin. Tinea cruris refers to the infection of the groin. While tinea corporis and cruris occurs worldwide, they are most common in tropical and subtropical regions. The free availability and misuse of potent topical steroid-containing creams also containing an antifungal and antibacterial agent have become the bane of dermatologists in developing countries.
Trichophyton rubrum is the most common agent worldwide, followed by T. mentagrophytes .
There is an ongoing epidemic like situation of widespread, often inflammatory recalcitrant dermatophytosis in South Asia, Middle Eastern countries and several countries in Europe due to a specific genotype of T. mentagrophytes complex called T. mentagrophytes ITS genotype VIII/Indian genotype (Nenoff et al.) It is known to be associated with terbinafine resistance and is responsive to itraconazole in higher doses for a higher duration.
The current Indian epidemic of superficial dermatophytosis due to Trichophyton mentagrophytes - a molecular study
Nenoff P, Verma SB, Vasani R, et al. Mycoses. 2019; 62: 336–356.
Management Strategy
Topical therapies are the first line of defense when treating localized tinea corporis and tinea cruris. Oral antifungal treatments are recommended in extensive, recurrent, or chronic infections not responsive to topical antifungal treatment, especially against the backdrop of topical steroid abuse. Topical therapies alone may be a judicious choice in special situations in which oral antifungals are contraindicated, as in patients with comorbidities and concomitant medications that contraindicate antifungals, in infants, and in the first trimester of pregnancy. Some preventative measures, including educational programs, maintaining proper hygiene, avoiding communal areas, and using antimicrobial fabrics, may help limit relapse and prevent transmission.
Specific Investigations in Superficial Dermatophytosis
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Direct microscopy on KOH (potassium hydroxide) specimens
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Fungal culture
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Molecular diagnosis
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Dermoscopy
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Antifungal susceptibility testing and genomic analysis
Epidemiological aspects of dermatophytosis in Khuzestan, southwestern Iran, an update
Rezaei-Matehkolaei A, Rafiei A, Makimura K, et al. Mycopathologia 2016; 181(7–8): 547–53.
This was a 1-year survey where 4120 skin, hair, and nail samples obtained from outpatients with symptoms suggestive of tinea were analyzed using direct microscopy, culture, and molecular sequencing. T. interdigitale (58.7%) was the predominant isolate followed by Epidermophyton floccosum (35.4%), Microsporum canis (3%), T. rubrum (1.5%), Trichophyton species of Arthroderma benhamiae (0.5%), T. tonsurans (0.3%), and T. violaceum (0.3%).
Reappraisal of conventional diagnosis for dermatophytes
Pihet M, Le Govic Y. Mycopathologia 2017; 182(1–2): 169–80.
Tinea corporis and intertriginous lesions should be scraped from the edge using a dermal blunt curette (Brocq curette) rather than a scalpel blade. Swabbing following scraping is recommended in inflammatory or oozing lesions.
Direct microscopic examination in 10% potassium hydroxide mount is an efficient screening technique that allows quick diagnosis to clinicians who can provide antifungal therapy pending culture results. Quality of specimen and skill of the observer determine the success of mycological examination. False negative results are seen in 15%–30% in routine practice.
Fungal culture is used for definitive identification but often lacks sensitivity, is time consuming, and identification of filamentous fungi at the species level using morphological characteristics needs experienced staff.
Molecular techniques are being increasingly employed in the clinical microbiological laboratories for identification and direct detection of organisms in clinical specimens because of high sensitivity and specificity and small turnaround time. Nucleic acid–based techniques are more specific than the phenotypic characteristics since genotypic characteristics are less affected by the external environment.
Dermoscopy can be helpful in identifying vellus hair involvement, and antifungal susceptibility testing and genomic analysis can document drug resistance. A plethora of reports and studies document terbinafine resistance in T. mentagrophytes and T. interdigitale .
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