LAUSR

We read with interest the article from Veasey et al. that reported a case of tinea nigra of the palm where reflectance confocal microscopy (RCM) was used to confirm the clinical diagnosis. Tinea nigra is a pigmented cutaneous superficial mycosis mainly caused by Hortaea werneckii. The typical clinical manifestation of this fungus is a single, brown to black asymptomatic macule with an irregular border mainly localized on palms or soles because infection is believed to occur as a result of inoculation from a contamination source such as soil, sewage, wood, or compost subsequent to trauma in the affected areas. Albeit being usually larger and lighter in color, these lesions tend to resemble acral nevi or melanoma, thus leading many clinicians to perform unnecessary biopsies. RCM is an emerging non-invasive imaging technique that can show hyphae as thin linear and hyper-reflective structures in the stratum corneum in cutaneous superficial mycosis, including tinea nigra and allows to confirm the clinical diagnosis and to avoid conventional mycological examinations and skin biopsies (Fig. 1). However, hyphae should be differentiated from the contours of normal keratinocytes that can form thin lines and from artifacts. Curiously, stellate hyper-reflective bodies are often visible in acral skin on RCM, possibly corresponding to keratinocytes membranes in a plane not parallel to the microscope tip. Fig. 2 shows normal acral skin of a healthy person where these artifacts are well visible and are identical to the images presented by Veasey et al. as hyphae of tinea nigra. The authors stated that hyphae identified by RCM in tinea nigra were tortuous, irregular, and short, different from the morphology of the thin and elongated hyphae of the dermatophytes. However, in our experience and in the other case of tinea nigra reported in the literature,