A so far incurable skin disease, in which scaly patches, circular in form, appear on the skin and gradually spread. Its progress is very slow and those attacked by it may live for years. It is contagious and was very serious in ancient times and in the Middle Ages, the only treatment being to keep the lepers separate. It is now rarely seen in civilized countries. Of recent years it has been severe in the Hawaiian Islands, where the lepers are all sent to a settlement on the island of Molokai.