Boni E. Elewski

A U.S. epidemiologic survey of superficial fungal diseases

BACKGROUNDnLarge-scale studies performed outside the United States have demonstrated that most cases of onychomycosis and tinea pedis are caused by dermatophytes, primarily Trichophyton rubrum. However, other studies have suggested that yeasts and nondermatophytic molds may play a role, particularly in onychomycosis.nnnOBJECTIVEnThis study was undertaken to determine the epidemiology of superficial fungal infections in a U.S. population.nnnMETHODSnFungal cultures were performed on patients with clinically suspected tinea cruris, tinea corporis, tinea capitis, tinea pedis, and onychomycosis.nnnRESULTSnDermatophytes were the most commonly isolated fungi in each type of superficial fungal disease studied. T. rubrum was the most commonly isolated dermatophyte species, although Trichophyton tonsurans was more common in tinea capitis and equally common in tinea corporis/tinea cruris. In tinea pedis and onychomycosis, dermatophytes appeared in approximately 95% and 82% of isolates, respectively. Candida albicans and nondermatophyte molds played only a minor role in onychomycosis; C. albicans was isolated in 7% of nail cultures and nondermatophytic molds were isolated in 11%.nnnCONCLUSIONnThese results are in general agreement with other major epidemiologic studies performed outside the United States. Dermatophyte fungi cause most superficial fungal infections.

Onychomycosis in children: Prevalence and treatment strategies

BACKGROUNDnOnychomycosis is observed less frequently in children than adults. Until recently management of onychomycosis in children included topical formulations, oral griseofulvin, and in some cases deferral of treatment.nnnOBJECTIVEnWe attempted to determine the prevalence of onychomycosis in North American children 18 years old or younger attending our dermatology offices (three Canadian, two U.S.) and to report the groups experience using fluconazole, itraconazole, and terbinafine for onychomycosis.nnnMETHODSnWe undertook a prospective, multicenter survey in which all children, regardless of presenting complaint, were examined for onychomycosis by a dermatologist. In instances of clinical suspicion appropriate nail samples were obtained for light microscopy and culture.nnnRESULTSnA total of 2500 children under age 18 were examined in the five-center survey (1117 males and 1383 females, mean +/- S.E. age: 11.2 +/- 0.1 years). There was one child with fingernail and ten with mycologically confirmed toenail dermatophyte onychomycosis. The overall prevalence of onychomycosis was 0.44%. Considering those children whose primary or referring diagnosis was not onychomycosis or tinea pedis, the prevalence of onychomycosis was 0.16%. Outside the survey we have seen six other children with dermatophyte onychomycosis; these 17 cases form the basis for the remainder of the report. Of the 17 children, eight (47%) had concomitant tinea pedis infection, and in 11 (65%) a sibling, parent, or grandparent had onychomycosis or tinea pedis. Management included topical terbinafine (two patients: one cured, one failed therapy), topical ketoconazole (one patient: clinical improvement), oral fluconazole (two patients: one cured, one had Downs syndrome and was noncompliant), oral itraconazole (four patients: three cured with subsequent recurrence at follow-up in one patient, one lost to follow-up), oral terbinafine (five patients: four cured with subsequent recurrence at follow-up in one patient, one failed therapy). One child received no therapy following discussion with the parents, one was lost to follow-up and one was found to have asymptomatic hepatic dysfunction with hepatitis C at pretherapy bloodwork.nnnCONCLUSIONnThe prevalence of onychomycosis in our sample of North American children 18 years old or younger was 0.44% (n = 2500). In the subset of children whose primary or referring diagnosis was not onychomycosis, the prevalence of onychomycosis was 0.16%. Children with onychomycosis should be carefully examined for concomitant tinea pedis, and their parents and siblings checked for onychomycosis and tinea pedis. The newer oral antifungal agents fluconazole, itraconazole, and terbinafine may be effective and well-tolerated in the treatment of onychomycosis in this age group. These drugs should be carefully evaluated in a larger cohort of children with onychomycosis.

Diagnostic techniques for confirming onychomycosis

Other nail diseases may mimic a fungal infection. Therefore the diagnosis of onychomycosis requires an assessment of both clinical and laboratory features. Onychomycosis is comprised of four distinct types, each of which requires a different technique to obtain a nail specimen. A potassium hydroxide (KOH) preparation may be used to confirm the presence of fungi. However, a fungal culture is required to identify the specific genus and species of the pathogen. It may be necessary to perform histopathologic analysis of the nail unit in cases in which the clinical appearance suggests the presence of a fungal nail infection, but the KOH preparation and culture are negative.

Optimal growth conditions for the determination of the antifungal susceptibility of three species of dermatophytes with the use of a microdilution method

As a prerequisite to standardization of dermatophyte susceptibility testing, conditions that support optimal growth of different dermatophyte species must be established. Eighteen isolates of Trichophyton spp. (T rubrum, T mentagrophytes, T tonsurans) were grown in 4 different media: RPMI 1640 with L-glutamine, without sodium bicarbonate and buffered at pH = 7.0; antibiotic medium #3 (Penassay); yeast nitrogen base with 0.5% dextrose buffered at pH = 7.0; and Sabouraud dextrose broth. Incubation for 6 days at 35 degrees C produced the following results: RPMI and Sabouraud dextrose supported equally sufficient growth for all strains tested; Penassay supported growth of only 33% of the isolates tested, and buffered yeast nitrogen base did not support growth of any isolates. RPMI was selected as the optimal medium, and organisms were tested at both 30 degrees C and 35 degrees C with a standardized inoculum density of 10(3) conidia/mL. No temperature differences were noted in the amount of growth of the dermatophytes tested. With RPMI at an incubation temperature of 35 degrees C, 3 inoculum sizes (10(3), 10(4), and 10(5) conidia/mL) were tested against 4 antifungal agents: griseofulvin, itraconazole, terbinafine, and fluconazole. Inoculum size did not affect minimum inhibitory concentration (MIC) results for itraconazole or terbinafine, but a larger inoculum produced a slightly higher MIC for griseofulvin and a noticeably higher MIC for fluconazole. Our data support the use of RPMI 1640, 35 degrees C, and 4 days as an incubation temperature and time, respectively, and an inoculum of 10(3) conidia/mL as optimal conditions for the determination of the antifungal susceptibility of dermatophytes.

Onychomycosis caused by Scytalidium dimidiatum

We report a case of onychomycosis caused by Scytalidium dimidiatum (syn., Hendersonula toruloidea) in a patient who did not live in an endemic area. This nondermatophyte mold may produce disease indistinguishable from dermatophyte fungi, but it does not respond to current systemic antimycotic therapy. Distal subungual onychomycosis, lateral onycholysis followed by lateral nail plate invasion, and chronic paronychia are common nail presentations.

Treatment of tinea capitis: beyond griseofulvin☆☆☆★

Tinea capitis is a common pediatric scalp infection caused by dermatophytes. Topical therapy alone is ineffective, so oral griseofulvin has traditionally been the standard treatment. The new antimycotic agents itraconazole, terbinafine, and fluconazole represent effective treatment alternatives that have fewer problems with tolerability and adverse effects. More comparative studies are needed to determine the optimal treatment with these agents and adjuvant therapies such as antifungal shampoos, topical antimycotic agents, and corticosteroids.

Treatment of tinea capitis with itraconazole

This trial examined tiie use of itraconazole in patients with tinea capitis who were eitiier unresponsive to or unable to tolerate griseofulvin therapy.

Asthma induced by allergy to Trichophyton rubrum

The worldwide incidence of asthma and of allergic respiratory diseases is increasing (Akiyama K.‘Environmental allergens and allergic diseases.’Rinsho Byori 1997;45(1):13. DAmato G, Liccardi G, DAmato M. Environment and development of respiratory allergy. II. Indoors. Monaldi Arch Chest Dis 1994;49(5):412. Weeke AR. Epidemiology of allergic diseases in children. Rhinol Suppl 1992;13:5. Ulrik CS, Backer V, Hesse B, Dirksen A. Risk factors for development of asthma in children and adolescents: findings from a longitudinal population study. Respir Med 1996;90(10):623.) This has been attributed to several factors, including lifestyle changes and an expanding variety of potential causative allergens. Management of asthma entails preventive and acute medications, immunologic therapies, and removal of the identified allergen(s) from the patients environment. Without the latter, patients may not experience full symptomatic relief. This case report describes a patient who developed bronchial asthma subsequent to an infection of tinea pedis and pedal onychomycosis; antifungal management resulted in full resolution of his tinea pedis, onychomycosis and asthma.

Update on the safety of itraconazole pulse therapy in onychomycosis

As the use of newer antifungal agents becomes more widespread, safety issues surrounding their use have become more important. To date, the safety profile of itraconazole has been well defined by its worldwide use in 50 million patients over the past 13 years. Data from clinical practice and clinical trials indicate that the 1-week pulse regimen of itraconazole is well tolerated and associated with a favourable safety profile. Adverse events are generally mild and transient. Furthermore, a dose increase to 400 mg in the pulse regimen has had no adverse impact on safety.