The    recessive   genetic
   disorder  xeroderma  pigmentosum  results  in defective NER and cannot
   repair the thymine dimers from UV damage.
   The 4-year-old boy shows marked skin lesions, including two cancers on
   his nose.
   The  18-year-old  girl  on the right has been carefully protected from
   sunlight  since  her  diagnosis of XP in infancy; several cancers have
   been removed.