The word "keloid" refers to the irregular, abnormally protruding scar tissue that formed during the healing process in the burned skin of atomic bomb survivors. The name comes from the fact that the scars look like the shell and legs of a crab.
Appearing often in persons exposed to the bombing about two kilometers from the hypocenter, keloids formed four months after the bombing and became most prominent 6 to 14 months thereafter. Most of the scars shrank and healed after about two years.
[Shirabe R and Tezuka H: Hiroshima Igaku 12,1959]
Number of keloid cases by distance from the hypocenter