By Gary M. White, MD
Pigmentary demarcation lines, also known as Futcher's lines or Voigt's lines, are physiological lines which correspond to a border of abrupt transition between the more deeply pigmented outer skin and the lighter colored inner skin. The etiology is unknown, but they have been considered as an atavistic remnant, where the dorsal skin is pigmented more than the ventral to provide better protection from the sun. Various types have been described, with B being the most common. It commonly develops during pregnancy and regresses after delivery.
A sharp demarcation between the outer darker and inner lighter skin is characteristic on the arm of a black patient. It represents a congenital difference in the darkness of pigment and one theory suggests that the dorsal skin is more heavily pigmented to provide better protection from the sun. Such a difference may become more obvious during pregnancy. A similar finding may be seen on the posterior thighs.
No treatment is needed.
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