<prompt> Xeroderma pigmentosum is caused due to:DNA synthesis defectEctodermal cell migration defectAbnormal nucleotide excision repairMelanocyte proliferation  <response>: Xeroderma pigmentosum XP is a rare autosomal recessive disease characterized by photosensitivity, pigmentary changes, premature skin ageing, neoplasia and abnormal Nucleotide excision repair. Ref: Rooks textbook of dermatology, 8th edition, Pg15.71. 