Scalp pseudomycetoma caused by Microsporum canis in an immunocompetent pediatric patient

R.G. Vitale1, M. Larralde1, A. Castillo1, M.E. Abad1, P. Boggio1, M. Label1, M.C. Corbella1, J. Afeltra1, J.F. Meis2, R.G. Vitale1

Author address: 

1Ramos Mejí­a Hospital, BUENOS AIRES, CABA, Argentina 2Canisius-Wilhelmina Hospital, NIJMEGEN, The Netherlands


Introduction: Pseudomycetoma is an extremely infrequent deep skin and subcutaneous tissue infection due to dermatophytes that mainly affect the scalp of children and is commonly preceded by a long-term tinea capitis. Clinical case: A 13-year-old girl presented with a 6 months history of two asymptomatic nodules on her scalp. Physical examination revealed diffuse white scale and alopecia suggestive of tinea capitis. Two erythematous firm nodules, 1 to 1.5 cm of diameter were also observed that were initially interpreted as inflammatory pilomatrixomas. The patient started oral griseofulvin at a daily dose of 20 mg/kg. After 3 months of treatment, scalp desquamation and alopecia resolved, but the nodules persisted and increased in size and number. One of them was surgically removed and was sent for histological and mycological evaluation. Histopathology showed a normal epidermis and the presence of aggregates of fine basophilic granules embedded in a homogeneous eosinophilic matrix surrounded by a giant cell granulomatous reaction in the deep dermis. Periodic Acid Schiff (PAS) stain revealed that those granules consisted of hyphal aggregates. Direct mycological examination showed hyaline hyphae, but culture on SGA, DTM after 3 weeks of incubation and several subcultures to different media, with extended incubation periods, developed only sterile mycelia. Then, with this criterion, since the fungus could not be identified, molecular methods were employed. The obtained ITS sequence of the isolate proved to be 100% identical to Microsporum canis sequences. Therefore, diagnosis of scalp pseudomycetoma caused by Microsporum canis was confirmed. Acquired immunodeficiency was discarded. The remaining nodules were all surgically excided, and medical treatment was rotated to oral terbinafine, 10 mg/kg/daily, during 7 months. After 5 months of follow-up the girl is free of lesions. Discussion: Fungal mycetoma is chronic infection of the skin and subcutaneous tissues characterized by tumefactive and indurated nodular growth, draining sinus tracts and macroscopically visible granules. Mycetoma of the scalp due to dermatophytes is called "œpseudomycetoma"and is an extremely infrequent entity in humans. It clinically differs from eumycotic mycetomas in that there are larger lesions, may affect other sites of the body than hands and feet, and do not have fistulae. Additional features include the presence of pseudogranules as well as different histopathological findings. However, direct self-inoculation of the microorganism through scratches may also play a role in the pathogenesis of this disease. We herein report an additional case of pseudomycetoma due to Microsporum canis in an immunocompetent girl, associated with tinea capitis with a good response to combined surgical and medical antifungal treatment. To our knowledge, only 4 pediatric cases of pseudomycetoma attributable to Microsporum canis have been described in the literature.

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Full conference title: 

4th Trends in Medical Mycology
    • TIMM 4th (2012)