The Peculiar Demarcation of Pigmentation along the So‐called Voigt's Line among the Japanese

Summary Rare cases of a phenomenon in which there is a sharp demarcation between the hyperpigmented surface of the extensors and the less pigmented skin of the flexors, rather than the normal gradual transition, have been observed among the Japanese. This demarcation may be found on various parts of the body but is most commonly seen on the extremities, where it follows the direction of the so‐called Voigt's line. This phenomenon appears to affect females ten times as frequently as males; it is found in all age groups. Three interesting questions are posed—does this phenomenon occur among peoples other than the Japanese? Does it serve as a barrier against the spread of other skin disorders which occur of along its line? Finally, what is the mechanism underlying this condition?