DermNet NZ

Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Blaschko lines

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.

Blaschko's lines Blaschko's lines
Blaschko's 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
Inflammatory linear verrucous naevus
Lichen striatus
Lichen striatus
Linear porokeratosis
Linear porokeratosis
Childhood conditions distributed along Blaschko lines on limb
Linear lichen planus
Lichen planus
Lichen striatus
Lichen striatus/Blasckitis
Linear telangiectasia
Telangiectasis confined to left arm during pregnancy
Adult conditions distributed along Blaschko lines on limb
Epidermal naevus
Epidermal naevus
Lichen planus
Lichen planus
Blaschko lines on trunk

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

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