They may look like astronauts doing their weekly shop but the spacesuit-like headgear protects Thomas and Vincent Seris from deadly exposure to ultraviolet (UV) light.

Seris twins Xeroderma Pigmentosum XP
French twins Thomas and Vincent Seris wear their protective masks while shopping in BordeauxRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Thomas and Vincent Seris wear masks to protect them from UV light emitted by halogen or neon lightsRegis Duvignau/Reuters

The French twins were born with a rare condition called Xeroderma Pigmentosum (XP). Any exposure to the sun's rays could cause fatal skin cancers. They are not only at risk outdoors: artificial lights such as halogen and neon lights can also emit UV light.

Colloquially referred to as Children of the Night (Les Enfants de la Lune) they were diagnosed with the one-in-a-million genetic condition when they were two years old. Vincent had three bouts of skin cancer within the first four months following diagnosis.

The two boys had to wear ski masks, coveralls and thick gloves whenever they went outside. Now they are testing a new ventilated, transparent mask. Developed by several French hospitals, it is hoped the mask will eventually be made available to some of the estimated 5,000 to 10,000 XP sufferers around the world.

Seris twins Xeroderma Pigmentosum XP
French twins Vincent and Thomas and Seris pose in their protective masksRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Thomas and Vincent Seris take the tram into town in BordeauxRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Thomas and Vincent return from their shopping trip in BordeauxRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Vincent and Thomas leave their apartment in BordeauxRegis Duvignau/Reuters

The family lived with their shutters permanently drawn until their mother Françoise covered all of their windows with a UV-blocking film. Their school in Bordeaux also installed protective filters on their classroom windows, allowing the twins to have a normal education.

Thomas and Vincent are students at the University of Bordeaux, which has installed UV filters to allow them to attend classes.

Françoise has set up charity organisation Enfants de la Lune (Children of the Moon) to help others with the condition.

Seris twins Xeroderma Pigmentosum XP
The twins chat to a student at the university in BordeauxRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Vincent uses a device to check for ultraviolet light while his brother holds a maskRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Vincent Seris holds a dosimeter, a device that checks the level of ultraviolet lightRegis Duvignau/Reuters
Seris twins Xeroderma Pigmentosum XP
Vincent (left) and Thomas Seris pose on the street in BordeauxRegis Duvignau/Reuters