(C) Gene repair defectHUMAN DISEASE & DNA REPAIR DEFECTDiseaseCancer susceptibilitySymptomsAtaxia telangiectasiaLymphomasTelangiectases in skin & eyes, immune dysfunctionBloom syndromeCarcinomas, leukaemias, LymphomasFacial telangiectases, photosensitivityFanconi anemiaLeukaemiasPancytopeniaXeroderma pigmentosumSkin carcinomas, melanomasSkin and eye photosensitivity, keratoses[?]Diseases associated with defective DNA repair systemAtaxia telangiectasiaBloom syndromeCockayne's syndromeProgeria (Hutchinson-Gilford Progeria syndrome)Rothmund-Thomson syndromeTrichothiodystrophyWerner syndromeXeroderma pigmentosumHereditary non-polyposis colon cancer.Human Diseases of DNA Damage RepairDefective Non-homologous End Joining Repair (NHEJ)Severe combined immunodeficiency diseaseRadiation sensitive severe combined immunodeficiency disease (RS-SCID)Defective Homologous Repair (HR)AT-like disorder (AT LD)Nijmegen breakage syndrome (NBS)Bloom syndrome (BS)Werner syndrome (WS)Rothmund-Thomson syndrome (RT S)Breast cancer susceptibility 1 & 2 (BRCA1, BRCA2)Defective DNA Nucleotide Excision Repair (NER)Xeroderma pigmentosumCockayne syndrome (CS)Trichothiodystrophy (TT D)Defective DNA Base Excision Repair (BER)MUTYH-associated polyposis (MAP)Defective DNA Mismatch Repair (MMR)Hereditary Non-polyposis Colorectal Cancer (HNPCC)ATAXIA-TELANGIECTASIAClinical Symptoms (ATM+)Cerebellar Ataxia (Neuromotor Dysfunction)Dilation of blood vesselsPremature agingImmunodeficiencyGonadal AtrophyCellular Phenotypes (ATM+)Genomic instabilityPoor cell growthDefective cell-cycle checkpointsRadio-sensitivityCancer predispositionlymphoma,leukemia (ATM+)Breast (ATM+)Inactivation of the ATM gene leads to ataxia-telangiectasia (A-T)Ataxia refers to poor coordination & Telangiectasia to small dilated blood vessels, both of which are hallmarks of the disease.A child who has inherited A-T will display nervous system abnormalities by age 2, and will then progressively lose muscle control.