Blaschko lines

What are the Blaschko lines?

Blaschko lines or the lines of Blaschko are thought to represent pathways of epidermal cell migration and proliferation during the development of the fetus.

History of the lines of Blaschko

This concept was first described by the German dermatologist Alfred Blaschko in 1901 at the 7th Congress of German Dermatological Society.

These lines constitute a surface pattern that is distinguished from other morphological lines of the skin and skin dermatomes. They do not correspond to the nervous system or vascular pathways.

What is the distribution of Blaschko lines?

Blaschko lines are consistently V-shaped on the upper spine, S-shaped on the abdomen, inverted U-shaped from the breast area to the upper arm, and perpendicular down the front and back of the lower extremities.

They never cross the anterior truncal midline but run along it.

These lines are invisible but many inherited and acquired diseases of skin manifest themselves according to these patterns creating the visual appearance of these lines.

Blaschko's lines 

Blaschko's lines 

Which skin conditions are distributed along Blaschko lines?

Many inherited and some acquired skin conditions are distributed along Blaschko lines.

Table 1. Congenital skin disorders

Table 2. Acquired skin disorders

Childhood conditions distributed along Blaschko lines on a limb

Inflammatory linear verrucous naevus 

Lichen striatus 

Linear porokeratosis 

Adult conditions distributed along Blaschko lines on a limb

Lichen planus 

Lichen striatus/blaschkitis 

Telangiectasis confined to left arm during pregnancy 

Blaschko lines on the trunk

Epidermal naevus 

ILVEN 

Lichen planus