Blaschko lines follow embryotic cell migration patterns and are seen in some mosaic genetic disorders such as incontinentia pigmenti and pigment mosaicism. Dermatomal distributions are lines on the skin surface following the distribution of spinal nerve roots. The rash caused by herpes zoster (Shingles) follows such dermatomal lines. History
The Koebner phenomenon was named after the rather eccentric but renowned German dermatologist Heinrich Koebner (1838–1904). Koebner is best known for his work in mycology. His intense nature is illustrated by the following: in a medical meeting, he proudly exhibited on his arms and chest three different fungus infections, which he had self-inoculated, in order to prove the infectiousness of the organisms he was studying. The Koebner phenomenon is the generalized term applied to his discovery that on psoriasis patients, new lesions often appear along lines of trauma. See also
Renbök phenomenon

References
Sources
Crissey JT, Parish LC, Holubar KH. Historical Atlas of Dermatology and Dermatologists. New York:  The Parthenon Publishing Group, 2002. Paller A, Mancini A.  Hurwitz Clinical Pediatric Dermatology. Philadelphia: Elsevier Saunders, 2002.
Fairy tales can have variants where one tale has an evil mother and the other an evil stepmother: in The Six Swans by the Brothers Grimm and also in The Wild Swans by Hans Christian Andersen, the heroine is persecuted by her husbands mother and in another one by her stepmother, and in The Twelve Wild Ducks, by his stepmother. Sometimes this appears to be a deliberate switch: The Brothers Grimm, having put in their first editions versions of Snow White and Hansel and Gretel where the villain was the biological mother, altered it to a stepmother in later editions, perhaps to mitigate the storys violence. Another reason for the change from a villainous mother to a villainous stepmother may have been the belief that mothers were sacred, as well as the belief that people would not believe that a mother could harbor such ill-will and animosity toward their child. The Icelandic fairy tale The Horse Gullfaxi and the Sword Gunnfoder features a good stepmother, who indeed aids the prince like a fairy godmother, but this figure is very rare in fairy tales. The stepmother may be identified with other evils the characters meet.