2. Gender differences in tinea capitis due to M canis
(or rarely, M gypseum or M hominis) are controversial. At
the beginning of the Microsporum spp infection era, girls
were 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 than
girls.8,9 The results of another large study in Austria showed
no predilection of gender.3 Studies on tinea capitis
performed in Mexico10 and Brazil11 slightly favor infections
in girls compared with boys. The general conclusion is that
there is no significant predilection in gender for Micros-
porum spp infection of the scalp in children, but in patients
aged older than 16 years, women were infected more
frequently then men, with a ratio ranging from 3:1 to 6:1.12,13
Changes in clinical pattern
Tinea capitis
A significant increase in the incidence and a change in the
clinical pattern of tinea capitis has been observed in recent
decades.14 For example, the frequency of M canis infection
in Croatia (Mediterranean and Central Europe) ranged from
1 case in the year 1978 verified by culture to 328 positive
cultures in 2008 based on our own data from the Reference
Laboratory for Dermatological Mycology and Parasitology
of the Ministry of Health and Social Welfare of the Republic
of Croatia of the University Department of Dermatology and
Venereology in Zagreb. Children aged 2 to 7 years were the
most commonly affected, but an increase in tinea capitis in
adults and elderly individuals was also observed.1,3 The
scalp was involved in about 30% of these cases, with the
clinical pattern of superficial tinea capitis with the small
spored ectothrix type. The typical features consisted of
patchy erythema with small adherent scales and irregularly
loose hairs.
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 with
thick crusts (Figures 1 and 2) due to Microsporum spp,
were observed in the Reference Laboratory instead of
T mentagrophytes, which was the expected pathogen in
those cases.14 M canis was isolated in 52 cases and M
gypseum in 6. Similar reports have come from other
countries 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. The
clinical diagnosis was confirmed by positive results on the
potassium 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 patients
with kerion caused by M canis were boys, aged 3 to 11
years, with a clinical evolution of 2 to 3 months.
Histopathologic examination showed various forms of
suppurative folliculitis (Figure 3).15
A report from Mexico documented 14 of 19 cases of
kerion were caused by M canis, T mentagrophytes was
isolated in 3 cases, and T tonsurans in 2.16 Although kerion
celsi and M canis infection, in general, most commonly
affect prepubertal children, it may also appear in newborn
infants and in very small children (Figure 4). An example of
this is a report of a 40-day-old girl with kerion due to M
canis. The source of infection was easily identified because
both parents had tinea corporis caused by M canis and no
pets were present at home.17
A few cases of favic invasion of glabrous skin and scalp
due to Microsporum spp have been reported,18 including an
8-year-old immunocompetent white girl with a 3-week
history of itchy scaling of the scalp associated with hair loss.
The absence of a more inflammatory clinical form was
explained by the short duration of symptoms. The source of
infection was a dog that had an unrecognized M canis
Fig. 1 Deep-seated kerion celsi-type tinea capitis caused by
Microsporum canis. Note the tumorous mass and the follicular
involvement.
Fig. 2 Extensive kerion celsi-type tinea capitis caused by Mi-
crosporum canis with involvement of the face and forehead.
147The changing face of Microsporum spp infections
3. infection. It was unclear why M canis caused a favic
invasion. One hypothesis is that the susceptibility for a favic
invasion depends on the patient's immune status as well as
on the virulence of the specific dermatophyte.
Onychomycosis
Onychomycosis by dermatophytes is usually caused by
Trichophyton spp; however, a certain number of cases
have been reported secondary to M canis.19 Clinical
presentation 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 canis
usually does not invade nails, and onychomycosis could be
explained by the altered immune status of the patient rather
than by a virulent strain of the dermatophyte.
M canis seems to be responsible for a great number of
disseminated and generalized dermatophytoses in HIV/ADS
patients. It could be expected that anthropophilic species
such as T rubrum or T mentagrophytes would be more
frequently involved.20 The reason for this phenomenon is not
entirely understood. One explanation is that a poor response
of M canis to topical antifungal agents and some systemic
azoles allows the infection to persist.20 Infections caused by
Microsporum spp generally represent a greater therapeutic
problem than Trichophyton spp. Our data from the results of
a 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 caused
by M canis was described in a 56-year-old diabetic man with
a 3-month history of erythematous papules and pustules on
his neck and face, with hair loss in the beard area, previously
treated with topical steroids. The source of infection was
presumed to be the patient's dog.22 Lesions with a lupuslike
and erythema annularelike (Figure 5) tinea incognito pattern
due to M canis have been also described.23
We have also reported the case of a 3-year-old girl with
more than 60 solitary and confluent annular skin lesions
due to M canis extensively involving the scalp and the
glabrous skin.7
A certain number of mycetomas24 and pseudomyceto-
mas25 due to M canis, as well as mixed infections with T
mentagrophytes,26 have been also reported, but we believe
that these sporadic examples reflect the broad spectrum of
clinical possibilities rather than significant changes in the
clinical pattern.
Treatment considerations
In most cases of glabrous skin involvement such as with
tinea pedis or manus, topical antimycotic treatment should be
sufficient, providing that the predisposing factors such as
diabetes, immunodeficiency, antibiotic treatment, separation
of the intertriginous regions, and proper clothing have been
successfully managed. Tinea capitis, however, represents a
Fig. 3 Suppurative folliculitis (kerion celsi-type tinea capitis) due
to Microsporum canis.
Fig. 4 Forehead infection due to Microsporum canis in a 2-year-
old child.
Fig. 5 Confluent lesions due to Microsporum canis in a
previously unrecognized tinea faciei (tinea incognito) treated with
topical steroids.
148 M. Skerlev, P. Miklić
4. clear indication for systemic antimycotic therapy. Tinea
capitis caused by M canis has been recognized as difficult to
treat. Lower cure rates were achieved compared with
infections caused by Trichophyton spp.27 This may be partly
due to the small-spored ectothrix nature of the infection,
which makes it difficult for drugs to access. The treatments
of choice are oral antifungal agents such as fungicidal
terbinafine and, traditionally, griseofulvin, especially its
microlyophilized form.
Some reports have indicated that Microsporum infections
may require a longer duration of treatment for eradication
than Trichophyton infections, and that short-term terbinafine
treatment is not always associated with adequate cure
rates.21,28 The optimal dosing regimen and treatment
duration of terbinafine for Microsporum-related tinea capitis
has yet to be established, and a higher dose than labeled by
the manufacturer might be required to cure this infection.21,28
In the first stage of treatment of the kerion type of tinea
capitis, antibacterial and antimycotic agents should be
topically applied in combination with oral antimycotics.
The effectiveness of concomitant administration of oral
steroids to modify the intensity of the inflammatory response
resulting in scarring has not been completely defined.29,30
The proper diagnosis and treatment of kerionlike mycoses
due to Microsporum spp will prevent nonindicated surgical
procedures in children (Figure 6).31
Fungistatic itraconazole is also a good therapeutic
option32 for this form of inflammatory tinea. The child's
age might be a limiting factor, because solutions with this
antifungal sometimes have emetic properties. Shampoos
containing tar may be applied as a concomitant treatment.
Conclusions
Significant changes in epidemiology, etiology, and the
clinical pattern of Microsporum spp infections that require
appropriate diagnostic and treatment strategy have been
observed. The data on significant changes in the prevalence
and clinical pattern of fungal skin infections due to Micros-
porum spp are rather controversial, depending on patient
lifestyle and geography. There must be greater awareness of
these changes to establish the proper diagnosis and treatment
to achieve the cure of the fungal infection.
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