Dermoscopic Differentiation of Blister Beetle Dermatitis and Herpes Zoster: an Observational Study.

Introduction: Blister beetle dermatitis (BBD) and herpes zoster (HZ) manifest suddenly with vesicular lesions mimicking each other and progress rapidly. But a lack of definite differentiating criteria yearns the need for better investigating modality. Though histopathology persuades the need, is an invasive procedure, commonly deferred. Thus, dermoscopy, a non-invasive rapid diagnostic tool, can help in differentiating.

Objectives: To evaluate different dermoscopic patterns of BBD and HZ to differentiate both and to study dermoscopic features in early and late stages of lesions.

Methods: An observational cross-section study conducted in southern India. Nine patients with clinical features suggestive of BBD and HZ were recruited. Lesions were divided arbitrarily into early and late. Dermoscopic examination was performed with handheld dermoscope. Diagnosis was confirmed by skin biopsy and Tzanck smear wherever necessary. Statistical analysis performed using data in terms of frequencies and percentages.

Results: Dermoscopy of early BBD lesions showed multiple discrete and confluent yellowish-white structures, brown dots, roundish white globules, gray structures, 'targetoid pattern', brown areas over intense reddish pink background. Late BBD lesions revealed pinkish-white area, reduced gray structures and, dotted and globular vessels. Early HZ lesions showed poly-lobular gray and brown globules, bright pink background, gray globules covered by grayish veil-like structure with gray rim. Late HZ lesions revealed 'solar eclipse' pattern and 'crumpled fabric' patterns. The dermoscopic findings correlated with histopathology.

Conclusions: Dermoscopic patterns show peculiar features consistently pertaining to BBD and HZ, thus help in early diagnosis assisting in accurate treatment in both conditions.