Clinics in Dermatology (2010) 28, 146–150

THE CHANGING FACE OF MICROSPORUM SPP INFECTIONSEdited by Mihael Skerlev, MD, Phd, Paola Miklić, MD

The changing face of Microsporum spp infectionsMihael Skerlev, MD, PhD⁎, Paola Miklić, MD

University Department of Dermatology and Venereology, Zagreb University Hospital Centre andZagreb University School of Medicine, Šalata 4, 10000 Zagreb, Croatia

Abstract Significant changes in epidemiology, etiology, and the clinical pattern of mycotic infectionscaused by Microsporum spp have been observed in recent years. Fungal infections caused by M canis,followed by M gypseum and M hominis, involving skin and its appendages, represent one of the mostcommon diseases worldwide and a recalcitrant problem in dermatology that demands appropriatediagnostic and treatment strategies. The most striking clinical phenomena of superficial and kerion andother forms of tinea, such as tinea capitis, fungal infections of the glabrous skin (tinea pedis, manus,cruris et corporis), and even onychomycosis due to Microsporum spp are described, with emphasis onthe changes that have occurred in the last decade. The data on significant differences in the prevalenceand clinical pattern of the fungal skin infections caused by Microsporum spp today compared with thedata at the beginning of the epidemic breakout might still be rather controversial, depending also on thepatients' lifestyle and geography. In general, physicians should be aware of the clinical spectrum ofmycotic infections due to Microsporum spp to avoid mistakes in identifying the fungal etiology and toprovide patients with the proper therapy.© 2010 Elsevier Inc. All rights reserved.

Introduction

Superficial fungal infections are of great importance indermatologic practice. The clinical appearance of lesionsconsistent with fungal infections may simulate otherdermatologic entities, making the diagnosis difficult.1

Fungal infections caused by Microsporum spp involvingboth the skin and the appendages represent one of the mostcommon diseases and a challenging problem in dermatolo-gy.2 Significant changes in epidemiology, etiology, and theclinical pattern of mycotic infections due to Microsporumspp have recently been observed. The most striking clinicalphenomena are described, taking into consideration thesignificant differences and specificities. Some changes havebeen observed in the epidemiology of Microsporum spp

⁎ Corresponding author.E-mail address: mskerlev@kbc-zagreb.hr (M. Skerlev).

0738-081X/$ – see front matter © 2010 Elsevier Inc. All rights reserved.doi:10.1016/j.clindermatol.2009.12.007

infections; however, the most significant have been detectedin the clinical pattern.

Changes in epidemiology

Microsporum spp, especially M canis, are one of themost commonly reported causative agents of dermatomy-coses worldwide, especially in Europe, including theMediterranean and Central Europe, and major parts ofAsia, Africa, and South America.3 In North America andthe United Kingdom, however, tinea capitis is predomi-nantly caused by Trichophyton tonsurans.4 Cats and dogsare the main reservoir of M canis as well as some othermammalian species, including rabbits.3 Human-to-humaninfection has been recorded in neonatal and intensive careunits.5,6 According to one of these reports multiple patientswere infected, and the source of infection was traced to aninfected nurse.6

147The changing face of Microsporum spp infections

Gender differences in tinea capitis due to M canis(or rarely, M gypseum or M hominis) are controversial. Atthe beginning of the Microsporum spp infection era, girlswere considered to be affected more frequently than boys.2,7

The results of some more recent European studies, however,showed that boys were more commonly affected thangirls.8,9 The results of another large study in Austria showedno predilection of gender.3 Studies on tinea capitisperformed in Mexico10 and Brazil11 slightly favor infectionsin girls compared with boys. The general conclusion is thatthere is no significant predilection in gender for Micros-porum spp infection of the scalp in children, but in patientsaged older than 16 years, women were infected morefrequently then men, with a ratio ranging from 3:1 to 6:1.12,13

Fig. 2 Extensive kerion celsi-type tinea capitis caused by Mi-crosporum canis with involvement of the face and forehead.

Changes in clinical pattern

Tinea capitis

A significant increase in the incidence and a change in theclinical pattern of tinea capitis has been observed in recentdecades.14 For example, the frequency of M canis infectionin Croatia (Mediterranean and Central Europe) ranged from1 case in the year 1978 verified by culture to 328 positivecultures in 2008 based on our own data from the ReferenceLaboratory for Dermatological Mycology and Parasitologyof the Ministry of Health and Social Welfare of the Republicof Croatia of the University Department of Dermatology andVenereology in Zagreb. Children aged 2 to 7 years were themost commonly affected, but an increase in tinea capitis inadults and elderly individuals was also observed.1,3 Thescalp was involved in about 30% of these cases, with theclinical pattern of superficial tinea capitis with the smallspored ectothrix type. The typical features consisted ofpatchy erythema with small adherent scales and irregularlyloose hairs.

Fig. 1 Deep-seated kerion celsi-type tinea capitis caused byMicrosporum canis. Note the tumorous mass and the follicularinvolvement.

During the last 8 years, 58 cases of typical kerion celsi,a deep-seated mycosis of the scalp (tinea profunda capillitii)clinically characterized by a tumorous mass covered withthick crusts (Figures 1 and 2) due to Microsporum spp,were observed in the Reference Laboratory instead ofT mentagrophytes, which was the expected pathogen inthose cases.14 M canis was isolated in 52 cases and Mgypseum in 6. Similar reports have come from othercountries with a high prevalence of M canis infection.15

There were 15 boys and 4 girls (age range, 2-12 years)reported with a clinical diagnosis of kerion celsi. Theclinical diagnosis was confirmed by positive results on thepotassium hydroxide (KOH) examination and by culture.The most commonly isolated dermatophyte was M canis(32%), followed by T mentagrophytes (27%), T tonsurans(21%), T rubrum (10%), and M gypseum (5%). All patientswith kerion caused by M canis were boys, aged 3 to 11years, with a clinical evolution of 2 to 3 months.Histopathologic examination showed various forms ofsuppurative folliculitis (Figure 3).15

A report from Mexico documented 14 of 19 cases ofkerion were caused by M canis, T mentagrophytes wasisolated in 3 cases, and T tonsurans in 2.16 Although kerioncelsi and M canis infection, in general, most commonlyaffect prepubertal children, it may also appear in newborninfants and in very small children (Figure 4). An example ofthis is a report of a 40-day-old girl with kerion due to Mcanis. The source of infection was easily identified becauseboth parents had tinea corporis caused by M canis and nopets were present at home.17

A few cases of favic invasion of glabrous skin and scalpdue to Microsporum spp have been reported,18 including an8-year-old immunocompetent white girl with a 3-weekhistory of itchy scaling of the scalp associated with hair loss.The absence of a more inflammatory clinical form wasexplained by the short duration of symptoms. The source ofinfection was a dog that had an unrecognized M canis

Fig. 3 Suppurative folliculitis (kerion celsi-type tinea capitis) dueto Microsporum canis.

148 M. Skerlev, P. Miklić

infection. It was unclear why M canis caused a favicinvasion. One hypothesis is that the susceptibility for a favicinvasion depends on the patient's immune status as well ason the virulence of the specific dermatophyte.

Onychomycosis

Onychomycosis by dermatophytes is usually caused byTrichophyton spp; however, a certain number of caseshave been reported secondary to M canis.19 Clinicalpresentation included distal subungual onychomycosis,onychodystrophy, and proximal subungual onychomycosis.Some of these patients were receiving oral steroid therapy,whereas others were diagnosed with HIV/AIDS. M canisusually does not invade nails, and onychomycosis could beexplained by the altered immune status of the patient ratherthan by a virulent strain of the dermatophyte.

M canis seems to be responsible for a great number ofdisseminated and generalized dermatophytoses in HIV/ADSpatients. It could be expected that anthropophilic speciessuch as T rubrum or T mentagrophytes would be morefrequently involved.20 The reason for this phenomenon is not

Fig. 4 Forehead infection due to Microsporum canis in a 2-year-old child.

entirely understood. One explanation is that a poor responseof M canis to topical antifungal agents and some systemicazoles allows the infection to persist.20 Infections caused byMicrosporum spp generally represent a greater therapeuticproblem than Trichophyton spp. Our data from the results ofa large multicenter study of tinea capitis caused by Micros-porum spp support the latter.21

Glabrous skin involvement

The rosacealike,22 tinea incognita clinical pattern causedbyM canis was described in a 56-year-old diabetic man witha 3-month history of erythematous papules and pustules onhis neck and face, with hair loss in the beard area, previouslytreated with topical steroids. The source of infection waspresumed to be the patient's dog.22 Lesions with a lupuslikeand erythema annularelike (Figure 5) tinea incognito patterndue to M canis have been also described.23

We have also reported the case of a 3-year-old girl withmore than 60 solitary and confluent annular skin lesionsdue to M canis extensively involving the scalp and theglabrous skin.7

A certain number of mycetomas24 and pseudomyceto-mas25 due to M canis, as well as mixed infections with Tmentagrophytes,26 have been also reported, but we believethat these sporadic examples reflect the broad spectrum ofclinical possibilities rather than significant changes in theclinical pattern.

Treatment considerations

In most cases of glabrous skin involvement such as withtinea pedis or manus, topical antimycotic treatment should besufficient, providing that the predisposing factors such asdiabetes, immunodeficiency, antibiotic treatment, separationof the intertriginous regions, and proper clothing have beensuccessfully managed. Tinea capitis, however, represents a

ig. 5 Confluent lesions due to Microsporum canis in areviously unrecognized tinea faciei (tinea incognito) treated withpical steroids.

Fpto

Fig. 6 Deep-seated (kerion celsi) tinea capitis caused by Mi-crosporum canis. Note the scar that resulted from an unnecessarysurgical procedure.

149The changing face of Microsporum spp infections

clear indication for systemic antimycotic therapy. Tineacapitis caused by M canis has been recognized as difficult totreat. Lower cure rates were achieved compared withinfections caused by Trichophyton spp.27 This may be partlydue to the small-spored ectothrix nature of the infection,which makes it difficult for drugs to access. The treatmentsof choice are oral antifungal agents such as fungicidalterbinafine and, traditionally, griseofulvin, especially itsmicrolyophilized form.

Some reports have indicated that Microsporum infectionsmay require a longer duration of treatment for eradicationthan Trichophyton infections, and that short-term terbinafinetreatment is not always associated with adequate curerates.21,28 The optimal dosing regimen and treatmentduration of terbinafine for Microsporum-related tinea capitishas yet to be established, and a higher dose than labeled bythe manufacturer might be required to cure this infection.21,28

In the first stage of treatment of the kerion type of tineacapitis, antibacterial and antimycotic agents should betopically applied in combination with oral antimycotics.The effectiveness of concomitant administration of oralsteroids to modify the intensity of the inflammatory responseresulting in scarring has not been completely defined.29,30

The proper diagnosis and treatment of kerionlike mycosesdue to Microsporum spp will prevent nonindicated surgicalprocedures in children (Figure 6).31

Fungistatic itraconazole is also a good therapeuticoption32 for this form of inflammatory tinea. The child'sage might be a limiting factor, because solutions with thisantifungal sometimes have emetic properties. Shampooscontaining tar may be applied as a concomitant treatment.

Conclusions

Significant changes in epidemiology, etiology, and theclinical pattern of Microsporum spp infections that requireappropriate diagnostic and treatment strategy have been

observed. The data on significant changes in the prevalenceand clinical pattern of fungal skin infections due to Micros-porum spp are rather controversial, depending on patientlifestyle and geography. There must be greater awareness ofthese changes to establish the proper diagnosis and treatmentto achieve the cure of the fungal infection.

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