Evaluation of Diagnostic Efficacy of Polarized and Ultraviolet-Induced Fluorescent Dermoscopy in Dermatophyte Infections

Abstract Context: The diagnostic accuracy of ultraviolet fluorescent (UVF) dermoscopy in identifying dermatophyte infection remains to be elucidated. Aims: to assess the dermoscopic features and diagnostic accuracy of UVF dermoscopy in tinea capitis and tinea of other parts of the skin. Settings and Design: A cross-sectional comparative study was performed on 119 dermatophytosis cases. Methods and Materials: Fifty-one cases of tinea capitis and 68 cases of tinea of other sites. Dermoscopic examination was performed using both polarized and UV-induced fluorescence settings. Then, scales along the lesion’s edge were scraped, and fluorescent hair was plucked for microscopic examination with KOH. Results: For tinea capitis, ectothrix hair invasion was found in 45 (88.2%) cases, and endothrix in 6 (11.8%) cases. Polarized dermoscopy findings in ectothrix were Morse code-like hair (93.3%), zigzag hair (23.5%), and whitish sheath (17.8%), while corkscrew and comma hairs were found in endothrix. UVF dermoscopy showed peripilar green fluorescence in all cases with ectothrix hair, with a sensitivity of 88.2% and a positive predictive value of 100%. In tinea of other sites, the main dermoscopic findings were white scales in 70.6% of cases peripherally, 47.1% perifollicular, and 8.8% within skin furrows. 53% of lesions showed evidence of damaged hair. In the UVF setting, peripilar green fluorescence was observed in 44.1% of vellus hair. The sensitivity and positive predictive value of UVF dermoscopy were 44.1% and 100%, respectively. Conclusions: UVF dermoscopy accurately discriminates between endothrix and ectothrix hair in tinea capitis and identifies vellus hair involvement in tinea of other parts of the skin.