Abstract:
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.
2009
abstract No:
P136
Full conference title:
4th Trends in Medical Mycology
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- TIMM 4th (2012)