Bygum et al.
blaschko lines
The most credible explanation for this phenomenon seems to lie in embryonic development, a phase in which cells migrate and proliferate.
It may be hard to believe — not least because you don’t see them — but the truth is that human skin is full of stripes, the so-called blaschko lines, which are believed to map the movement of cells since the body was developing in the womb. However, and here is the key to the enigma, these stripes are only visible on very specific circumstances.
The name of the phenomenon was attributed to the researcher responsible for its identification. Alfred Blaschko, a German dermatologist, spent years collecting data from patients with skin diseases, in which the distribution of skin lesions was described. In 1901, after years of study, the conclusions were finally presented in a conference.
More than a century later, scientists agree that the most credible explanation for this phenomenon lies in the fetal develop, in a phase in which the cells migrate and proliferate. The aforementioned researcher would have managed to draw the lines on a Greek statue that was integrated into his study at the time.
According to the representation, the stripes never cross the anterior midline, that is, the imaginary limit running the length of the chest It’s from abdomen along the front of the body. On the back, they form a shape that matches the letter Vand there are also wavy lines along the limbs and around the head and face.
According to IFL Sciencethere is a set of diseases that can give rise to pigmentation lesions that follow the lines of blaschko, as is the case of striatum lichen, pigmentary incontinence and McCune-Albright syndrome. In fact, skin diseases that tend to replicate blaschko’s lines are an example of cutaneous mosaicism.
Genetic mutations in a subset of skin cells mean that the human body is home to two different populations of skin cells — with similarly different genetic material. At the points where the two different cell lines meet, injuries which coincide with the Blaschko lines.
A specific type of mosaicism is the chimerism. In chimeras, the two different sets of genetic material result from two different fertilized eggs. although the mosaicism is quite common, chimeraism is Very rare in nature.
In humans, for example, chimeras can sometimes arise when a fraternal twin absorbs the brother while the embryos are developing in the womb — the surviving twin may not even be aware of their unusual genetic makeup until later in life.
Still according to the same site, one of the main signs of chimera is the difference in pigmentation. Chimeras can manifest themselves through different colored eyes, but also through skin pigmentation patterns that follow Blaschko’s lines.
ZAP // 
