What is Xeroderma Pigmentosum, due to which an 11-yr-old boy in Spain can't stay under Sun?

An 11-year-old boy in Spain's Barcelona suffers from Xeroderma Pigmentosum (XP), due to which he can't stay under Sun. It's a rare genetic disorder causing hypersensitivity to UV light and eye problems. People with XP develop sunburns easily and have higher risk of skin cancer. Symptoms include blistering sunburns, dry and thin skin (xerosis), and freckling (lentigo) before age 2.