## Most Common Dermatophyte in Tinea Cruris **Key Point:** Trichophyton rubrum is the most common dermatophyte causing tinea cruris globally and in India, accounting for approximately 60–70% of cases. ### Epidemiology of Tinea Cruris | Dermatophyte | Prevalence | Geographic Notes | Clinical Features | |---|---|---|---| | **T. rubrum** | 60–70% | Most common worldwide, including India | Chronic, slowly progressive; well-demarcated borders | | E. floccosum | 15–20% | Common in tropical regions | Acute inflammation; may spread to buttocks | | T. mentagrophytes | 10–15% | Zoophilic; animal contact history | Vesicular, inflammatory variant | | M. canis | <5% | Zoophilic; rare in tinea cruris | Usually from cat/dog contact | **High-Yield:** T. rubrum is an **anthropophilic** dermatophyte with a predilection for warm, moist intertriginous areas (groin, axillae, inframammary folds). It is the most common cause of tinea corporis, tinea pedis, and tinea unguium as well. ### Clinical Pearl **Tip:** In tinea cruris caused by T. rubrum, lesions are typically chronic and less inflammatory. E. floccosum tends to cause more acute inflammation and may involve the buttocks ("tinea glutealis"). This clinical distinction can help predict the organism even before culture results. **Warning:** Do not confuse tinea cruris with candidiasis (caused by Candida albicans, a yeast, not a dermatophyte). Candidal intertrigo typically affects the natal cleft and is more macerated and erythematous. ### Mnemonic **TRY** — **T**richophyton **R**ubrum is the **Y**ield in tinea cruris. [cite:Robbins 10e Ch 25]
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