Polarized and Ultraviolet-induced Fluorescence Dermoscopy in Genital Nodular Scabies in Skin of Color: An Objective Tool for Diagnosis and Monitoring Treatment Response

Abstract Background: Nodular scabies is conventionally regarded as a post-scabietic hypersensitivity reaction rather than active infestation. Consequently, management often relies on treatment history. Polarised and ultraviolet-induced fluorescence (UVF) dermoscopy may provide objective evidence of persistent mites and guide therapy. Aims: To evaluate the frequency of mite and egg detection in genital nodular scabies using polarised and UVF dermoscopy and to assess its utility in differentiating treated from untreated lesions. Settings and Design: Cross-sectional observational study. Methods and Materials: The study included 120 male patients with genital nodular scabies, equally divided into treated and untreated groups. Dermoscopic examination was performed using a handheld dermoscope under polarised and UVF modes. Characteristic dermoscopic features were documented and correlated with potassium hydroxide examination. Statistical Analysis: Statistical analysis was calculated by SPSS software version 2.0. Percentages were used for representing qualitative data. Chi-square test was used for proportions in the qualitative data analysis. P< 0.05 was considered statistically significant. Results: Mites were detected in the majority of untreated patients (80%) and in a notable proportion of treated patients (28.3%). Dermoscopic features suggestive of active infestation, including the grey-edged line sign, UVF ball sign, bright white clod and wake-shaped scales, were observed more frequently in untreated cases. Wake-shaped scales were consistently identified under both polarised and UVF modes and appeared to be a reliable marker of ongoing mite activity. Scabietic eggs were detected more readily under UVF dermoscopy, particularly in treated patients, including some without demonstrable mites. Non-specific dermoscopic features were observed in both groups. Conclusion: Dermoscopy is useful in recognition of mite in scabetic nodules, to customize the treatment for better management.