Case report. Onychomycosis due to Microsporum canis
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44, 119±120 (2001)
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Case report. Onychomycosis due to Microsporum canis Fallbericht. Onychomykose durch Microsporum canis C. Romano1, E. Paccagnini2 and L. Pelliccia1 Key words. Microsporum canis, nail infection, itraconazole. SchluÈsselwoÈrter. Microsporum canis, Nagelinfektionen, Itraconazol.
Summary. A case of distal subungual onychomycosis of the big toe due to Microsporum canis is reported in a 69-year-old male asthma patient who had been treated with systemic corticosteroids for the last 3 years. The nail infection was contracted from a cat who was a healthy carrier. The patient was treated successfully with intermittent itraconazole therapy. Zusammenfassung. Es wird ein Onychomykose-Fall durch Microsporum canis bei einem 69jaÈhrigen Patienten beschrieben, welcher seit drei 3 Jahren wegen Asthma bronchiale mit Glukokortikoiden systemisch behandelt wurde. Als klinischer Befund war eine subunguale distale Onychomykose eines Fuûnagels zu beobachten. Der Pilzerreger wurde durch eine Katze uÈbertragen, die klinisch asymptomatisch erschien. Nach einer Pulstherapie mit Itraconazol kam es zur Abheilung.
Introduction There have been few reports in the literature of onychomycosis due to Microsporum canis [1±12] and in some cases medical history has revealed previous infection of glabrous skin and of scalp by the same dermatophyte [9±12] and contact 1
Istituto di Scienze Dermatologiche, and 2Istituto di Istologia ed Embriologia Generale, UniversitaÁ degli Studi di Siena, Italy.
Correspondence: Dr. Clara Romano, Via Monte Santo, 3, 53100 Siena, Italy. Tel.: +39 577 585422 Fax: +39 577 44238
with cats [9, 10]. Here we report the ®rst case observed in Siena, in which the principal agent of the dermatophytosis was M. canis, and cats, which are often healthy carriers, were the main source of infection . Case report The patient was a 69-year-old man with hypertension and asthma, who had been receiving systemic steroid therapy (methylprednisolone) for 3 years. At presentation, he was taking 8 mg dayx1 of the drug and had distal subungual hyperkeratosis of the right big toe, with yellowish coloration of the nail. The manifestations had been present for several months. There was no evidence of previous damage to the big toe nail. Dermatological examination failed to reveal dermatophyte infections in other parts of the body. Direct microscopic examination of pathological material from the nail, soaked in 30% KOH, revealed dermatophyte hyphae. When the material was sown on Sabouraud glucose agar with chloramphenicol and cycloheximide, colonies that were typical of M. canis developed. Scanning electron microscope examination of fragments of colonies provided more morphological details of the macroconidia, which were 27±30 mm long and 9±10 mm wide, and typical of M. canis. The patient, who denied any previous mycotic infections, had a 2-year-old Persian cat, apparently free of dermatophyte infections, which slept at the end of his bed. Microsporum canis was isolated from fur samples of the cat obtained by the Mackenzie technique .
C. R OMANO ET AL.
The patient was treated with intermittent itraconazole therapy at a dose of 400 mg dayx1, 1 week per month for 3 months, without any side-effects. Clinical and mycological recovery were achieved and con®rmed at follow-up 1 year later. The cat was successfully treated with 125 mg oral griseofulvin at a dose of half a tablet per day for 40 days. Discussion The clinical manifestations of the few cases of onychomycosis due to M. canis reported in the literature include distal subungual onychomycosis , onychodystrophy [9, 10] and proximal subungual onychomycosis . They are therefore similar to the manifestations of onychomycoses due to Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton ¯occosum, which are the usual agents of nail infections. The site of infection may be the nails of the feet or hands. Since M. canis does not usually attack nails, it is thought that infection is due to abnormal susceptibility of the host, due to depressed immune status, rather than to a particularly virulent strain of the fungus . In our case and that of Hughes , the patient had been on oral steroid therapy for several years. Bournerias reported a case in an HIV-positive patient with tinea capitis . Microsporum canis has also been isolated in apparently healthy nails of patients with acquired immunode®ciency syndrome . All recent cases have been successfully treated, mainly with different protocols of terbina®ne [9, 11] or itraconazole [10, 15]. In our case, the source of infection was traced to the patient's cat, con®rming that cats with healthy carrier status are a major source of contagion of dermatophyte infections in the Siena area . Close contact with the animal and immunosuppression due to steroid therapy are probably the reasons why Microsporum canis attacked the nail in the present case. In agreement with recent studies on itraconazole therapy of onychomycosis , we found that intermittent therapy was just as effective as the daily treatment used by AndreÂ .
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