Blaschko's Lines

Updated: Jul 28

Do Humans Have Stripes?


This article aims to increase health practitioners' awareness about Blaschko's lines, its manifestation in certain medical conditions, and the importance of skin examination.


Figure 1: Blaschko's lines (12)


Okay, not precisely stripes, the lines of Blaschko are a pattern of lines on the skin that represent the developmental growth pattern during epidermal cell migration. The lines are distinguished from other morphological lines of the skin and do not represent vascular, lymphatic or nervous structures. All humans are suspected to have Blaschko's lines which are invisible to the naked eye. These patterns may however become visible in certain skin conditions such as linear sebaceous naevus, unilateral naevoid telangiectasia and in other acquired skin conditions such as lichen striatus and linear psoriasis where they may persist for 1 to 2 years (2).


When visible, Blaschko's lines can be S-shaped, V-shaped, wavy, striped or linear (1). They are speculated to develop during the embryonic stage, but their origin is still not fully understood (3). The pattern itself could be created because specific cells or groups of cells react differently to certain skin conditions.


The German dermatologist Dr Alfred Blaschko conceptualised these skin patterns more than a century ago, it is however Dr Douglas Montgomery, an American dermatologist who first proposed that the linear pattern of epidermal nevi reflects “streams” of tissue growth during embryogenesis. He hypothesised that skin conditions that followed the Blaschko lines are manifestations of cutaneous mosaicism where there’s clinical contrast between genetically normal and abnormal skin(1). This pattern can be observed in congenital skin conditions such as adrenal hypoplasia, CHILD syndrome, albinism death syndrome and Menkes syndrome (4).

 


Figure 2: Patterns of the skin according to Blaschko's lines. (a) Type 1a: linear (many X-linked traits). (b) Type 1b: broad linear (many X-linked traits). (c) Type 2: lateralization or checkerboard pattern (as in congenital hemidysplasia with Ichthyosiform erythroderma and limb defects (CHILD) syndrome, for example). (d) Type 3: phylloid (leaf-like) pattern (11)