I never knew of this condition, which affects only French people. From Wikipedia:

Dromomania, also called travelling fugue, is a psychological condition in which people spontaneously depart their routine, travel long distances and take up different identities and occupations. Months may pass before they return to their former identities.

The most famous case was that of Jean-Albert Dadas, a Bordeaux gas-fitter. Dadas would suddenly start travelling, on foot, and come to as far away as Prague or Vienna or even Moscow with no memory of his travels.

Only a handful of cases were ever documented, nearly all in France in the late nineteenth century.

Read also: Fugue-itive minds and bodies