Pigmentary demarcation lines separate normal zones of light and darker skin colour. They are more obvious in some people than in others and are symmetrical, arising on both sides of the body.
Where are pigmentary demarcation lines found?
Pigmentary demarcation lines have been described in 6 areas.
Between lateral and medial aspects of upper arm
Face: lateral cheek and periorbital skin
What do pigmentary demarcation lines look like?
Different shades of skin colour may first be noticed in infancy and persist into adulthood. The most common site, PDL-A, is darker on the outer aspect of the arm than the medial aspect. The contrast between the two colours may be more noticeable following sun exposure.
What is the cause of pigmentary demarcation lines?
Pigmentary demarcation lines occur in all races and skin types. There is a genetic predisposition to more-or-less obvious variation in skin pigmentation. The separation of zones correspond to Blaschko lines, indicating they are a common manifestation of cutaneous mosaicism.