Blaschko-linear Becker’s naevus over lower limb: A case study and literature review

Becker’s naevus (BN) presents as a unilateral, hyperpigmented patch with hypertrichosis over the upper trunk/proximal upper extremity. Usually, block-like/geographical pattern is seen; however, linear forms have also been reported. A 21-year-old man presented to us with a history of hyperpigmented, well to ill-defined discrete-to-coalescent plaques with brownish macules scattered at the periphery, over posteromedial aspect along Blaschko’s lines, extending from the buttock to the ankle of the right lower limb. No associated hypertrichosis/focal defects were seen. On dermoscopy (10×, DermLite DL4W, Dana Point, California) pigment network, scaling with perifollicular accentuation, perifollicular hypopigmentation, and uniform brown dots/globules/lines were seen. A skin biopsy revealed acanthosis and focal papillomatosis with increased pigment in the basal layer; pigment incontinence and melanophages were seen in the dermis. To the best of our knowledge, only one such case has been reported with Blaschko-linear BN over the lower limb. We present here an uncommon case of Blaschko-linear BN over the lower limb with dermoscopy and a concise literature review of BN over the lower limb.