GD08: Dermoscopy as a tool to differentiate vitiligo from other hypopigmenting disorders: a cross-sectional comparative study

Ananya Sharma, Binod K. Khaitan, Vishal Gupta, M. Ramam and Kanika Sahni

All India Institute of Medical Sciences, New Delhi, India

Hypopigmented skin lesions are an important cause of psychological morbidity. The dermoscopic features of hypopigmenting disorders apart from vitiligo are not well-characterized. The aim of this study was to evaluate the utility of dermoscopy as a tool to distinguish between different entities presenting with hypo- or depigmented skin lesions. We conducted a cross-sectional study including 105 lesions of vitiligo and 137 lesions of other hypopigmenting disorders, which comprised 14 different conditions such as ash-leaf macule (ALM; n = 17), naevus depigmentosus (n = 16), postinflammatory hypopigmentation (n = 16), pityriasis alba (n = 15), pityriasis versicolor (n = 14), idiopathic guttate hypomelanosis (IGH; n = 14), lichen sclerosus (n = 12), leprosy (n = 9), piebaldism (n = 6), postinflammatory hypopigmentation (n = 16) and others. Dermoscopy by at least two dermatologists was done using a handheld dermoscope of × 10 magnification, in a maximum of three lesions in each patient. A complete absence of pigment network was 10 times more likely to be seen in vitiligo (66·7%) than a nonvitiligo disorder (30·7%; P < 0·001). Perifollicular retention of pigment had a specificity of 93·9% for vitiligo. A vascular pattern was observed more frequently in lesions in the vitiligo group (42·8%) than in the nonvitiligo group (21·1%; P < 0·001). Loss of discernibility of eccrine openings within the lesion was a pointer to vitiligo (P < 0·001). Scaling was seen almost exclusively in lesions of the nonvitiligo group. Leucotrichia was seen not only in 30·8% of vitiligo lesions, but also in 7·8% of nonvitiligo lesions. In the nonvitiligo group, naevus depigmentosus (n = 16) lesions were mostly hypopigmented with a faint pigment network throughout the lesion. In 15 of 17 (88·2%) ALMs, the pigment network had a characteristic pattern of sharply demarcated areas of normal network with jagged margins within the depigmented lesion, which had a negative predictive value of 99·1% for the diagnosis of ALM against all other diagnosis included in this study. Almost all IGH lesions (n = 14) had a sharply defined margin with completely absent pigment network, with eccrine openings discernible as white dots within 64·3% lesions. To conclude, a complete absence of pigment network, perifollicular retention of pigment, leucotrichia, presence of a vascular pattern, lack of discernibility of eccrine openings within the lesion and lack of scaling emerged as dermoscopic pointers towards the diagnosis of vitiligo over its other mimickers. Among the nonvitiligo group, conditions like ALM, naevus depigmentosus and IGH have characteristic features on dermoscopy, some of them being almost pathognomonic.