The dermatophytes, or ringworm fungi, include a group of fungi that have the ability to infect and survive only on dead keratin, the top layer, of skin, hair, and nails. The dermatophytes are ubiquitous in the environment and tinea infections are among the most common dermatologic disorders in the world. Dermatophytes are classified into three genera: Microsporum, Trichophyton, and Epidermophyton. The prevalent species of dermatophytes change with time and geographic location. The organisms may invade both the stratum corneum and the terminal hair shaft. Transfer of the organism may occur through the shedding of scales, autoinoculation, or transfer of spores. Microsporum canis is a frequent cause of tinea infections in children and is transferred from affected cats, dogs, horses, or cattle. Clinically, infections caused by dermatophytes are classified by the affected body region.
The history and physical exam will often establish the diagnosis of a dermatophyte infection. The use of laboratory resources, such as direct visualization of branching hyphae under a microscope, culture, or Wood's light examination, increases diagnostic accuracy.
In many cases of tinea infections, topical antifungal treatment is efficacious. Oral antifungal therapy is needed to efficaciously treat tinea capitis and tinea barbae when large portions of the body are involved or if the patient is immunocompromised. Combination antifungal and corticosteroid preparations are widely used by physicians for the treatment of superficial tinea infections. These preparations include an antifungal agent in combination with a mid-to high-potency steroid. The proposed mechanism of these agents is to treat the symptoms in addition to the dermatophyte infection. Physiciansareoftenunawareofthepotencyofthesteroidcomponentofthese preparations and, thus, their potential for local and systemic complications. Furthermore, the use of topical steroids for tinea infections may prolong the course of treatment.
Topical corticosteroid therapy suppresses inflammation and gives the patient and physician the false impression that the lesion is improving, whereas the fungal infection continues to flourish in the face of an altered immunologic defense. Following cessation of steroid treatment, the rash will return and may be transformed into an unrecognizable skin eruption, referred to as tinea incognito. The lesion may be characterized by the absence of scaling or a well defined border, diffuse erythema, scattered papules or pustules, and brown hyperpigmentation. Hyphae are easily demonstrated and can be seen a few days after discontinuing the use of a topical steroid.
Alston SJ, Cohen BA, Braun M. Persistent and recurrent tinea corporis in children treated with
combination antifungal/corticosteroid agents. Pediatrics. 2003;111:201–203.
Drake LA, Dinehart SM, Farmer ER, et al. Guidelines of care for superficial mycotic infections
of the skin: tinea capitis and tinea barbae. Guidelines/Outcomes Committee. American
Academy of Dermatology. J Am Acad Dermatol. 116;34(2 Pt 1):290–294.
Stein DH. Tineas–superficial dermatophyte infections. Pediatr Rev.1998;19(11):368–372.
Weinstein A, Berman B. Topical treatment of common superficial tinea infections. Am Fam
Physician. 2002;65(10):2095–2102.
Review other book chapters online related to Tinea cruris:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6 
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