Sock-line hyperpigmentation

Sock-line hyperpigmentation is a benign and acquired condition in infants. The lesions usually appear between the third month and the second year after birth and are asymptomatic. The defining characteristics of such lesions are the hyperpigmentation, linear or circular, unilateral or bilateral, and the horizontal distribution, preferentially located between ankle and knee. The differential diagnosis includes secondary wounds to physical abuse, linear or circular hyperpigmentation in infants, and acquired raised bands in infants. We introduce the particular case of a six month old-breastfeeding baby with wounds in both legs that show different reactions to the different level of pressure arising from dissimilar sock models, what supports the tight posttraumatic connection of this condition. Although the precise physiopathologic mechanism is unknown, the inflammatory reaction in the dermis or secondary paniculitis to the pressure coming from the elastic bands of socks that heal with postinflammatory changes can be argued.