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Tinea nigra is a superficial mycosis whose diagnosis is confirmed by isolating the infectious agent Hortae werneckii through mycological examinations. In vivo reflectance confocal microscopy, initially used in melanocytic dermatosis, has been used with skin infectious diseases to identify the parasite at the cellular level. We report, for the first time in the scientific literature, the use of reflectance confocal microscopy in a case of tinea nigra and compare its findings to dermoscopy and mycological examination results.
We report a patient with an asymptomatic macula in the palmar region (Figure 1). Due to the hypothesis of tinea nigra, we performed a dermoscopy examination. The results showed a non-melanocytic pattern with speckled and superficial pigmentation that did not follow the dermatoglyphs (Figure 2).1-3 Direct mycological examination (DME) revealed septate and dematiaceous tortuous hyphae and the fungal culture isolated the agent Hortae werneckii (Figure 3), confirming the diagnosis of tinea nigra.1,4
Before collecting samples for mycological examination, we performed an in vivo reflective confocal microscopy (RCM) of the lesion, which showed to a lesser extent linear structures with high reflectivity of speckled appearance, similar to the ones revealed by dermoscopy.2,3,5-7 The image showed that the speckled aspect, when isolated, was morphologically similar to the hyphae identified on DME (Figure 4).
In vivo reflective confocal microscopy (RCM) is a valuable method for evaluating pigmented and oncological lesions. The method fills the limitations of dermoscopy by displaying structural details similar to those seen on histopathological examinations. Recent studies have described the efficacy of RCM in identifying the infectious agent in vivo in infectious diseases.5,7 However, no scientific publications are found about its use for tinea nigra diagnosis. Therefore, this is the first report to do so.
In the present study, we identified that the fungus is hyperreflective, possibly due to the melanin present in its cell wall. The fibrillar aspect described with dermoscopy corresponds to the vegetative mycelium of the fungus. It is worth mentioning that the aspect of the hyphae identified in RCM is tortuous, irregular, and short, similar to that found in DME, and different from the morphology of the thin and elongated hyphae of the dermatophytes visualized in both DME and RCM.
Conflict of interest: none.
*Work performed at Dermatology Clinic at Hospital Santa Casa de São Paulo - São Paulo (SP), Brazil.
Financial support: None.