Cutaneous Fungal Infections Caused by Dermatophytes and Non-Dermatophytes: An Updated Comprehensive Review of Epidemiology, Clinical Presentations, and Diagnostic Testing

Abstract

Cutaneous fungal infection of the skin and nails poses a significant global public health challenge. Dermatophyte infection, mainly caused by Trichophyton spp., is the primary pathogenic agent responsible for skin, hair, and nail infections worldwide. The epidemiology of these infections varies depending on the geographic location and specific population. However, epidemiological pattern changes have occurred over the past decade. The widespread availability of antimicrobials has led to an increased risk of promoting resistant strains through inappropriate treatment. The escalating prevalence of resistant Trichophyton spp. infections in the past decade has raised serious healthcare concerns on a global scale. Non-dermatophyte infections, on the other hand, present even greater challenges in terms of treatment due to the high failure rate of antifungal therapy. These organisms primarily target the nails, feet, and hands. The diagnosis of cutaneous fungal infections relies on clinical presentation, laboratory investigations, and other ancillary tools available in an outpatient care setting. This review aims to present an updated and comprehensive analysis of the epidemiology, clinical manifestations, and diagnostic testing methods for cutaneous fungal infections caused by dermatophytes and non-dermatophytes. An accurate diagnosis is crucial for effective management and minimizing the risk of antifungal resistance.

Keywords: clinical; cutaneous fungal infection; dermatophyte; diagnosis; epidemiology; microsporum; non-dermatophyte; onychomycosis; tinea; trichophyton.

Figure 1

Clinical presentations of cutaneous fungal infection. (A) Tinea capitis: Gray patch on the vertex of the scalp. (B) Tinea cruris: Multiple annular scaly erythematous patches on the groin. (C) Tinea incognito: Ring-within-a-ring appearance. (D) Tinea corporis: Annular scaly erythematous macule with inflammation on the right leg caused by Microsporum canis. (E) Tinea faciei: Multiple scaly erythematous concentric rings on the chin caused by Microsporum canis. (F) Tinea corporis: Multiple red-rubber-ring macules on the right arm caused by Trichophyton mentagrophytes. (G) Dorsal view of the right big toenail: Onychomycosis caused by Trichophyton mentagrophytes, showing dermatophytoma and longitudinal striae adjacent to the dermatophytoma. (H) Hyponychium view of the right big toenail of the same patient: Sulfur-nugget-like subungual debris (white arrow) concurrent with tinea pedis presenting as an annular scaly macule (black arrow).

Figure 2

Potassium hydroxide examination with the 40× objective revealing branching septate hyphae under a light microscope.

Figure 3

Histopathological analysis of nail clippings from Neoscytalidium dimidiatum-induced onychomycosis using periodic acid–Schiff staining. Microscopic examination at low power with the 4× objective (A) and high power with the 40× objective (B) revealing black-brown fungal hyphae invading the nail plate.

Figure 4

Kerion caused by Microsporum canis. (A) Clinical presentation: Solitary inflammatory mass with alopecia. (B) Wood’s light examination of the same patient: Blue-greenish fluorescence. (C) Wood’s light examination after 2 weeks of fluconazole treatment: Disappearance of fluorescence.