42 - chromosomal breakage syndromes

Table 1. Chromosomal Breakage Syndromes With Neoplasias Caused by Defective DNA Repair

Syndrome	Chromosome Breakage/ Hypersensitivity: Immunodeficiencies	Cancer Risk
Ataxia telangiectasia	TCRA: 14q11 TCRB: 7q35 IGH: 14q32 No increased SCE† but increased gaps and breaks, nonhomologous interchanges/ Roentgentherapy, ionizing radiation, radiomimetic compounds: decreased IgA, IgG2, IgG, IgE	Risk of neoplasia 38%; 85% are leukemias and lymphomas (B-cell). Young children have acute lymphoblastic leukemia of T-cell origin. Older children have T-cell leukemia. Risk for other cancers is increased 4-fold (2- to 3-fold increased risk for breast cancer in carriers).
Bloom syndrome <1%>	SCE 12-15 times higher, homologous interchanges, increased gaps and breaks./ UV, cancer chemotherapeutic agents: Decreased IgA and IgM, and/or IgG	Risk for leukemia, lymphoma, adenocarcinoma, and other cancers increased 5- to 8-fold.
Fanconi anemia	Increased gaps and breaks, 30% between nonhomologous chromosomes, clones with translocations./ UV, chemotherapeutic agents for immunosuppression, diepoxybutane, mitomycin C, other DNA-crosslinking agents	For aplastic anemia, risk is increased for pancytopenia, leukemia, acute myeloid leukemia, squamous cell carcinoma, medulloblastoma, Wilms tumor, breast cancer, and liver cancer.

Xeroderma pigmentosum

Increased gaps and breaks, increased SCE after UV/ UV XPG group may be sensitive to X-rays

1000-fold increased risk for squamous cell carcinoma, basal cell carcinoma, malignant melanoma, and fibrosarcoma, and 10- to 20-fold increased risk for other tumors

Immunoglobulin A, immunoglobulin G₂, immunoglobulin G, immunoglobulin E

†Sister chromatid exchanges