Cause
The disability originates with impaired functioning of the anterior horn cells of the lower cervical cord (lower neck), but the cause of the decline is not fully understood and is still considered unknown. Researchers, including Hirayama, believe that "forward displacement of the cervical dural sac and compressive flattening of the lower cervical cord during neck flexion" is the contributing factor. Studies consistently note a loss of normal neck curvature (the cervical lordosis) and compression of the cervical chord by the dural sac in forward flexion. "There is a debate about whether this condition represents a focal form of primary LMN degeneration (ie, a focal form of spinal muscular atrophy) or a local consequence of chronic compression from a dural expansion in the cervical spine. "A familial link has been found in a minor percentage of cases, including parent-child and sibling-sibling. Because of the unusual distribution of the disease, some researchers speculate that there could be an ethnic link. Diagnosis
The condition presents almost exclusively in 15- to 25-year-old adults experiencing weakness in hand and arm. A patient history and a neurological exam narrows down the possible diagnosis; this preliminary exam typically includes strength and reflex tests. Cold paresis (increased weakness in cold weather) is reported by most patients (> 80%). Fasciculations are reported as uncommon (< 20%) to common; larger tremors  are more consistently cited. Males are far more likely to be diagnosed with the condition.The disease is rare and several cited cases deviate from the expected norm, making diagnosis more difficult.
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.