Xeroderma pigmentosum

- autosomal recessive
- defect in nucleotide excision repair, leading to deficient repair of DNA damage by UV radiation and chromosome breakage (uv light cause formation of pyrimidine dimer and prevent enzyme DNA polymerase from replicating DNA strand beyond site of dimer formation)
- photosensitivity with severe sunburn
- suffer from multiple malignant cutaneous neoplasm at early age