DENOUEMENT—CONTINUED FROM P. 661

Abstract

The procedure was a potassium hydroxide examination of the scraped base of a vesicle. It revealed fungal hyphae . Trichophyton tonsurans was later isolated on Sabouraud's agar. Thus the diagnosis was tinea corporis (tinea faciei). The presentation in this patient of acute onset of vesicular rash raised the possibility of herpes simplex virus infection. Herpes simplex in the skin, eye or mouth, if untreated, can be associated with viral dissemination and encephalitis. Herpes simplex of the skin in a neonate might resemble such disparate entities as staphylococcal infection, neonatal melanosis, incontinentia pigmenti and erythema toxicum, among others.1 Tinea faciei is not included in the differential diagnosis of lesions resembling neonatal herpes infection in the standard textbooks.1, 2 Tinea (ringworm) is a dermatophyte infection of the keratinous tissues including skin, hair and nails. The dermatophytes are usually classified on the basis of their host tropism and on the environment in which they are primarily found. Species of the three genera Epidermophyton, Microsporum and Trichophyton are classified as anthropophilic (tropism for humans) including such species as Trichophyton tonsurans, Trichophyton rubrum and Epidermophyton floccosum; zoophilic (tropism for mammals or birds) including Microsporum canis; or geophilic (tropism for soil) including Microsporum gypseum. Tinea can also be classified, independently of the species involved, according to the anatomic site that is affected. Hence there is tinea corporis (face, trunk, major limbs), tinea capitis (scalp, eyebrows, eyelashes) and tinea cruris (groin), as well as tinea barbae, pedis, manuun or unguium.3 Tinea capitis is the most common dermatophytosis in childhood. In recent years there has been a change in the species that causes tinea capitis from Microsporum organisms to T. tonsurans. The latter now accounts for >90% of all infections.4 Dermatophyte infections are quite rare in neonates. When it occurs the incubation period may be quite short. There are reports of tinea infection as early as 2 to 3 days of life.5, 6 Snider et al.7 reported an outbreak of tinea caused by M. canis in a newborn nursery. The infections usually occur on the head (scalp and face) and on the trunk. The source may be an infected mother or sibling who spreads the organisms to the newborn by close contact or by fomites. This is particularly common with anthropophilic dermatophytes. Lesions have usually been present for several weeks at the time they are brought to the physician's attention. The patient reported herein was unusual because the lesions had been present only for a few hours when the patient was brought to the clinic. Reported cases of dermatophytes in the neonatal period that have been published in the English language literature have described erythematous papules appearing in the first days of life. The lesions slowly evolve into circinate erythematous plaques with diameters varying from 0.5 to 12 cm.4 The plaques usually have central clearing, slight peripheral scaling and active papular margins. In addition tinea capitis in young infants might present as pustules that sometimes evolve into crusty, boggy nodules and plaques (kerion).8 Atypical lesions that have been reported usually resemble seborrheic dermatitis without alopecia,9 atopic dermatitis, cutaneous candidiasis and bacterial infections.10 The most rapid method of diagnosis is KOH examination of clinical specimens. There are reported cases of multiple negative KOH examinations despite positive fungal cultures. Infection of the small vellus hairs, called vellus hair parasitism, is described as a cause of KOH-negative, culture-positive tinea faciei in children.4 Tinea faciei usually responds to topical antifungal therapy. Our patient was discharged home on 1% clotrimazole cream twice daily with slow resolution of the lesion in several weeks. Tinea should be considered in the differential diagnosis of vesicular lesions in the newborn period. Direct microscopy of the base of the vesicle with KOH preparation and isolation and culture should be considered before subjecting the patient to costly and inconvenient procedures and treatments.