Blaschko lines

Author: V.N.Hiromel de Silva, Registrar in Dermatology, Waikato Hospital, New Zealand, 2008.

What are 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.

Which skin conditions distributed along Blaschko lines?

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

Congenital skin disorders
X-linked dominant skin disorders
Epithelial naevi
Pigmentary disorders
Acquired skin disorders
Disorders with polygenic background

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