Answer of Dermatopathology Case 20

Dermatophyte Infection

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Abstracts:

Dermatophyte infections.Am Fam Physician. 2003 Jan 1;67(1):101-8.

Dermatophytes are fungi that require keratin for growth. These fungi can cause superficial infections of the skin, hair, and nails. Dermatophytes are spread by direct contact from other people (anthropophilic organisms), animals (zoophilicorganisms), and soil (geophilic organisms), as well as indirectly from fomites. Dermatophyte infections can be readily diagnosed based on the history, physical examination, and potassium hydroxide (KOH) microscopy. Diagnosis occasionally requires Wood's lamp examination and fungal culture or histologic examination.Topical therapy is used for most dermatophyte infections. Cure rates are higher and treatment courses are shorter with topical fungicidal allylamines than with fungistatic azoles. Oral therapy is preferred for tinea capitis, tinea barbae, and onychomycosis. Orally administered griseofulvin remains the standardtreatment for tinea capitis. Topical treatment of onychomycosis with ciclopiroxnail lacquer has a low cure rate. For onychomycosis, "pulse" oral therapy withthe newer imidazoles (itraconazole or fluconazole) or allylamines (terbinafine) is considerably less expensive than continuous treatment but has a somewhat lower mycologic cure rate. The diagnosis of onychomycosis should be confirmed by KOH microscopy, culture, or histologic examination before therapy is initiated, because of the expense, duration, and potential adverse effects of treatment.

Microscopically differentiating dermatophytes from sock fibers.J Am Acad Dermatol. 2009 Dec;61(6):1024-7.

BACKGROUND: Dermatophytes are responsible for a number of superficial fungal infections that affect millions worldwide. During microscopic observation apotassium hydroxide (KOH) fungal smear, various filamentous materials such as common textile fibers from socks can obfuscate proper discernment of dermatophytes. OBJECTIVE: To differentiate dermatophytes from 9 common sock fibers. METHODS: Nine different textile fiber samples were microscopically analyzed by using a KOH direct smear test; their defining structural features were compared and contrasted with those of dermatophytes. RESULTS: Although thereare several similarities, sock fibers tend to have a non-septate, uniformstructure which differentiates them from dermatophytes. Sock fibers are also significantly larger than dermatophytes and can be viewed better at lower magnifications. LIMITATIONS: There is a lack of sock samples with 100% textile fiber composition. Also, fibers were examined in a clean setting, without the detritus that normally accompanies dermatophytes in a clinical setting.CONCLUSION: While textile fibers may be present in KOH preparations, their general appearance typically differs from that of dermatophytes; an observer who is familiar with these distinctions will be able to differentiate between the two.

Dermatophytosis: a summary of dermatomycosis as a proposal for future revisionof the guidelines.Nippon Ishinkin Gakkai Zasshi. 2009;50(4):199-205.

In preparing guidelines for dermatomycosis (tinea, trichophytia,dermatophytosis), we have primarily summarized the disease types and treatments as described in 4 textbooks used in Japan and abroad. We present our classification draft based on these following descriptions. In Japan, any dermatophytosis other than favus or tinea imbricata is considered to be tinea,while outside Japan, favus and tinea imbricata are also classified as tinea.Tinea capitis is classified together with trichophytia superficialis capillitiiand kerion celsi, in a group that tends to include asymptomatic carriers. Most textbooks generally classify trichophytia profunda of the glabrous skin andgranuloma trichophyticum as subtypes of tinea corporis. Tinea faciei can easilybe misdiagnosed, but in many cases can be distinguished from tinea corporis byits specific clinical picture. Tinea unguium is regarded as one type of onychomycosis. We present a summary of dermatomycosis treatment as a proposal for future revision of the guidelines. One of the problems in the treatment of tinea capitis is that the safety of itraconazole (ITZ) and terbinafine hydrochloride(TBF) in children has not been established. Severity criteria for concomitant useof oral medications in the treatment of tinea pedis remains to should be established. Although many clinical studies concerning tinea unguium have beenpublished, 3 of the 4 textbooks we consulted clearly stated that most of thosestudies were conducted by pharmaceutical companies. Further studies on the etiology and disease severity of tinea unguium are needed.